Biology Final Study 1-9

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Which of the following about mobile genetic elements is true? (a) DNA-only transporons do not code for proteins but instread rely on transposases found in the cells that are infected by viruses (b) The two major families pf transposable sequences found in the human genome are DNA only transposons that move by replicative transoposition (d) During cut-and-paste transposition, the donor DNA will no longer have the mobile genetic element embedded in its sequence when transposition is complete

(d) During cut-and-past transpositon, the donor DNA will no longer have the mobile genetic element embedded in its sequence when transposition is complete

Which of the following is false? (a) The human genome is more similar to the orangutan genome than it is to the mouse genome (b) A comparison of genomes shows that 90% of the human genome shares regions of conserved synteny with the mouse genome (c) Primates, dogs, mice and chickens all have the same number of genes (d) Genes that code for ribosomal RNA share significant similarity in all eukaryotes except are much more difficult to recognize in archaea

(d) Genes that code for ribosomal RNA share significant similarity in all eukaryotes except are much more difficult to recognize in archaea

8-52 Which of the following statements about DNA methylation in eukaryotes is false? (a) Appropriate inheritance of DNA methylation patterns involves maintenance methyltransferase. (b) DNA methylation involves a covalent modification of cytosine bases. (c) Methylation of DNA attracts proteins that block gene expression. (d) Immediately after DNA replication, each daughter helix contains one methylated DNA strand, which corresponds to the newly synthesized strand.

(d) Immediately after DNA replication, each daughter helix contains one methylated DNA strand, which corresponds to the newly synthesized strand.

7-12 Unlike DNA, which typically forms a helical structure, different molecules of RNA can fold into a variety of three-dimensional shapes. This is largely because ___________________. (a) RNA contains uracil and uses ribose as the sugar. (b) RNA bases cannot form hydrogen bonds with each other. (c) RNA nucleotides use a different chemical linkage between nucleotides compared to DNA. (d) RNA is single-stranded.

(d) RNA is single-stranded.

Which of the following do you not expect to find in the set of genes found in all organisms on Earth? (a) DNA replication (b) DNA repair (c) protein production (d) RNA splicing

(d) RNA splicing

8-5 Which of the following statements about differentiated cells is true? (a) Cells of distinct types express nonoverlapping sets of transcription factors. (b) Once a cell has differentiated, it can no longer change its gene expression. (c) Once a cell has differentiated, it will no longer need to transcribe RNA. (d) Some of the proteins found in differentiated cells are found in all cells of a multicellular organism.

(d) Some of the proteins found in differentiated cells are found in all cells of a multicellular organism.

Which of the following statements of pseudogenes is false? (a) they code for microRNAs (b) They share significant nucleotide similarity with functional genes (c) They are no longer expressed in the cell (d) There are estimated to be around 20,000 in the human genome

(d) There are estimated to be around 20,000 pseudogenes in the human genome

7-23 Which of the following might decrease the transcription of only one specific gene in a bacterial cell? (a) a decrease in the amount of sigma factor (b) a decrease in the amount of RNA polymerase (c) a mutation that introduced a stop codon into the DNA that precedes the gene's coding sequence (d) a mutation that introduced extensive sequence changes into the DNA that precedes the gene's transcription start site

(d) a mutation that introduced extensive sequence changes into the DNA that precedes the gene's transcription start site

7-34 snRNAs ___________________. (a) are translated into snRNPs. (b) are important for producing mature mRNA transcripts in bacteria. (c) are removed by the spliceosome during RNA splicing. (d) can bind to specific sequences at intron-exon boundaries through complementary base-pairing.

(d) can bind to specific sequences at intron-exon boundaries through complementary base-pairing.

8-4 Which of the following is not a good example of a housekeeping protein? (a) DNA repair enzymes (b) histones (c) A TP synthase (d) hemoglobin

(d) hemoglobin

This newly discovered antibiotic resistance in E Coli is most likely due to ____________. (a) a mutation within a gene (b) a mutation within the regulatory DNA of a gene (c) gene duplication (d) horizontal gene transfer

(d) horizontal gene transfer

Which of the following would contribute most to successful exon shuffling? (a) shorter introns (b) a haploid genome (c) exons that code for more than one protein domain (d) introns that contain regions of similarity to one another

(d) introns that contain regions of similarity to one another

7-28 Total nucleic acids are extracted from a culture of yeast cells and are then mixed with resin beads to which the polynucleotide 5 - TTTTTTTTTTTTTTTTTTTTTTTTT-3 has been covalently attached. After a short incubation, the beads are then extracted from the mixture. When you analyze the cellular nucleic acids that have stuck to the beads, which of the following is most abundant? (a) DNA (b) tRNA (c) rRNA (d) mRNA

(d) mRNA

7-63 According to current thinking, the minimum requirement for life to have originated on Earth was the formation of a _______________. (a) molecule that could provide a template for the production of a complementary molecule. (b) double-stranded DNA helix. (c) molecule that could direct protein synthesis. (d) molecule that could catalyze its own replication.

(d) molecule that could catalyze its own replication.

7-5 Transcription is similar to DNA replication in that ___________________. (a) an RNA transcript is synthesized discontinuously and the pieces are then joined together. (b) it uses the same enzyme as that used to synthesize RNA primers during DNA replication. (c) the newly synthesized RNA remains paired to the template DNA. (d) nucleotide polymerization occurs only in the 5′-to-3′ direction.

(d) nucleotide polymerization occurs only in the 5′-to-3′ direction.

8-51 Which of the following is not a general mechanism that cells use to maintain stable patterns of gene expression as cells divide? (a) a positive feedback loop, mediated by a transcriptional regulator that activates transcription of its own gene in addition to other cell-type- specific genes (b) faithful propagation of condensed chromatin structures as cells divide (c) inheritance of DNA methylation patterns when cells divide (d) proper segregation of housekeeping proteins when cells divide

(d) proper segregation of housekeeping proteins when cells divide

8-55 Using genetic engineering techniques, you remove the sequences that code for the ribosome-binding sequences of the bacterial LacZ gene. The removal of these sequences will lead to ___________. (a) more LacZ protein produced due to faster ribosome movement across the LacZ mRNA. (b) transcriptional repression, resulting in fewer mRNA molecules produced from this gene. (c) a longer half-life for the LacZ mRNA. (d) translational inhibition of the LacZ mRNA.

(d) translational inhibition of the LacZ mRNA.

How many years ago did species M and N diverge from their last common ancestor?

10 million years ago

How many different splice isoforms could be produced for this gene?

120

Sometimes, chemical damage to DNA can occur just before DNA replication begins, not giving the repair system enough time to correct the error before the DNA is duplicated. This gives rise to mutation. If the cytosine in the sequence TCAT is deaminated and not repaired, which of the following is the point mutation you would observe after this segment has undergone two rounds of DNA replication? (a) TTAT (b) TUAT (c) TGAT (d) TAAT

7-26 Transcription in bacteria differs from transcription in a eukaryotic cell because __________________________. (a) RNA polymerase (along with its sigma subunit) can initiate transcription on its own. (b) RNA polymerase (along with its sigma subunit) requires the general transcription factors to assemble at the promoter before polymerase can begin transcription. (c) the sigma subunit must associate with the appropriate type of RNA polymerase to produce mRNAs. (d) RNA polymerase must be phosphorylated at its C-terminal tail for transcription to proceed.

(a) RNA polymerase (along with its sigma subunit) can initiate transcription on its own.

Which of the following regions of the genome is the least likely to be conserved over evolutionary time? (a) the upstream regulatory region of a gene that encodes the region conferring tissuse specificity (b) the upstream regulatory region of a gene that binds to RNA polymerase (c) The portion of the genome that codes for protein (d) The portion of the genome that codes for RNAs that are not translated into protein

(a) the upstream regulatory region of a gene that encodes the region conferring tissue specificity

8-64 The modular nature of the Eve gene's regulatory region means that ______. (a) there are seven regulatory elements and each element is sufficient for driving expression in a single stripe. (b) all the regulatory elements for each stripe use the same transcriptional activators. (c) the E. coli LacZ gene is normally only expressed in a single stripe—unlike Eve, which is expressed in seven stripes. (d) transcription regulators only bind to the stripe 2 regulatory DNA segment in stripe 2.

(a) there are seven regulatory elements and each element is sufficient for driving expression in a single stripe.

7-67 When using a repeating trinucleotide sequence (such as 5′-AAC-3′) in a cell- free translation system, you will obtain: (a) three different types of peptides, each made up of a single amino acid (b) peptides made up of three different amino acids in random order (c) peptides made up of three different amino acids, each alternating with each other in a repetitive fashion (d) polyasparagine, as the codon for asparagine is AAC

(a) three different types of peptides, each made up of a single amino acid

8-60 The extent of complementarity of a miRNA with its target mRNA determines ___________________________. (a) whether the mRNA will be immediately degraded or whether the mRNA will first be transported elsewhere in the cell before degradation. (b) whether the mRNA will be transported to the nucleus. (c) whether RISC is degraded. (d) whether the miRNA synthesizes a complementary strand.`

(a) whether the mRNA will be immediately degraded or whether the mRNA will first be transported elsewhere in the cell before degradation.

7-13 Which of the following molecules of RNA would you predict to be the most likely to fold into a specific structure as a result of intramolecular base-pairing? (a)5′CCCUAAAAAAAAAAAAAAAAUUUUUUUUUUUUUUUUAGGG-3′ (b)UGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUG-3′ (c) 5'-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA-3′ (d)5′GGAAAAGGAGAUGGGCAAGGGGAAAAGGAGAUGGGCAAGG-3′

(a)5′CCCUAAAAAAAAAAAAAAAAUUUUUUUUUUUUUUUUAGGG-3′

In humans and in chimps, 99% of the Alu retrotransposons are in corresponding positions. Which of the following is most likely explanation for this similarity? (a) The Alu retrotransposon is not capable of transposition in humans (b) Most of the Alu sequences in the chimps genome underwent gene duplication and divergence before humans and chimps diverged

(b)

Which of the following DNA sequences is not commonly carried on a DNA only transposon? (a) transposase gene (b) reverse transcriptase gene (c) recognition site for transposase (d) antibiotic-resistance gene

(b)

individual 1 is one of the parents of individual 2. The asterisk indicates the occurrence of a single mutation(in the germ line cell of zygote of individual 1).What is the chance that individual 2 will inherit the mutation in individual 1? (a) 100% (b) 50% (c) 1 in 100000 (d) none

(b) 50%

7-18 You have a piece of DNA that includes the following sequence: 5′-ATAGGCATTCGATCCGGATAGCAT-3' 3′-TATCCGTAAGCTAGGCCTATCGTA-5′ Which of the following RNA molecules could be transcribed from this piece of DNA? (a) 5′-UAUCCGUAAGCUAGGCCUAUGCUA-3′ (b) 5′-AUAGGCAUUCGAUCCGGAUAGCAU-3′ (c) 5′-UACGAUAGGCCUAGCUUACGGAUA-3′ (d) none of the above

(b) 5′-AUAGGCAUUCGAUCCGGAUAGCAU-3′

The nucleotide sequences between individuals differ by 0.1% yet the human genome is made up of about 3x10^9 nucleotide pairs. Which of the following is false? (a) In most human cells the homologous autosomes differ from each other by 0.1% (b) All changes between human individuals are single-nucleotide polymorphisms

(b) All changes between human individuals are single-nucleotide polymorphisms

Given the evolutionary relationship between higher primates shown the picture which of the following statements is false? (a) The last common ancestor of humans, chimps,gorillas and orangutans lived about 14 million years ago (b) Chimpanzees are more closely related to gorillas than humans (c) Humans and chimps diverged 6 million years ago (d) Orangutans are most divergent of the four species

(b) Chimpanzees are more closely related to gorillas than humans

7-30 Which of the following statements about RNA splicing is false? (a) Conventional introns are not found in bacterial genes. (b) For a gene to function properly, every exon must be removed from the primary transcript in the same fashion on every mRNA molecule produced from the same gene. (c) Small RNA molecules in the nucleus perform the splicing reactions necessary for the removal of introns. (d) Splicing occurs after the 5′ cap has been added to the end of the primary transcript.

(b) For a gene to function properly, every exon must be removed from the primary transcript in the same fashion on every mRNA molecule produced from the same gene.

Which of the following is false about the human genome? (a) about 1.5% of the human genome codes for exons (b) Only the exons are conserved between the genomes of humans and other mammals

(b) Only the exons are conserved between the genomes of humans and other mammals

7-24 There are several reasons why the primase used to make the RNA primer for DNA replication is not suitable for gene transcription. Which of the statements below is not one of those reasons? (a) Primase initiates RNA synthesis on a single-stranded DNA template. (b) Primase can initiate RNA synthesis without the need for a base-paired primer. (c) Primase synthesizes only RNAs of about 5-20 nucleotides in length. (d) The RNA synthesized by primase remains base-paired to the DNA template.

(b) Primase can initiate RNA synthesis without the need for a base-paired primer.

7-65 You are studying a disease that is caused by a virus, but when you purify the virus particles and analyze them you find they contain no trace of DNA. Which of the following molecules are likely to contain the genetic information of the virus? (a) high-energy phosphate groups (b) RNA (c) lipids (d) carbohydrates

(b) RNA

8-62 Which (a) The RNAi mechanism is found only in plants and animals. (b) RNAi is induced when double-stranded, foreign RNA is present in the cell. (c) RISC uses the siRNA duplex to locate complementary foreign RNA molecules. (d) siRNAs bind to miRNAs to induce RNAi.

(b) RNAi is induced when double-stranded, foreign RNA is present in the cell.

7-55 Which of the following statements about prokaryotic mRNA molecules is false? (a) A single prokaryotic mRNA molecule can be translated into several proteins. (b) Ribosomes must bind to the 5′ cap before initiating translation. (c) mRNAs are not polyadenylated. (d) Ribosomes can start translating an mRNA molecule before transcription is complete.

(b) Ribosomes must bind to the 5′ cap before initiating translation.

7-25 You have a bacterial strain with a mutation that removes the transcription termination signal from the Abd operon. Which of the following statements describes the most likely effect of this mutation on Abd transcription? (a) The Abd RNA will not be produced in the mutant strain. (b) The Abd RNA from the mutant strain will be longer than normal. (c) Sigma factor will not dissociate from RNA polymerase when the Abd operon is being transcribed in the mutant strain. (d) RNA polymerase will move in a backward fashion at the Abd operon in the mutant strain.

(b) The Abd RNA from the mutant strain will be longer than normal.

8-47 Which of the following statements about the Ey transcriptional regulator is false? (a) Expression of Ey in cells that normally form legs in the fly will lead to the formation of an eye in the middle of the legs. (b) The Ey transcription factor must bind to the promoter of every eye- specific gene in the fly. (c) Positive feedback loops ensure that Ey expression remains switched on in the developing eye. (d) A homolog of Ey is found in vertebrates; this homolog is also used during eye development.

(b) The Ey transcription factor must bind to the promoter of every eye- specific gene in the fly.

8-15 What do you predict would happen if you replace the Lac operator DNA from the Lac operon with the DNA from the operator region from the tryptophan operon? (a) The presence of lactose will not cause allosteric changes to the Lac repressor. (b) The Lac operon will not be transcribed when tryptophan levels are high. (c) The lack of glucose will no longer allow CAP binding to the DNA. (d) RNA polymerase will only bind to the Lac promoter when lactose is present.

(b) The Lac operon will not be transcribed when tryptophan levels are high.

Which species would be best to examine to determine what the sequence was in the last common ancestor of species X and S. cerevisiae? (a) Species V (b) species W (c) species Y (d) species Z

8-1 A neuron and a white blood cell have very different functions. For example, a neuron can receive and respond to electrical signals while a white blood cell defends the body against infection. This is because ______. (a) the proteins found in a neuron are completely different from the proteins found in a white blood cell. (b) the neuron and the white blood cell within an individual have the same genome. (c) the neuron expresses some mRNAs that the white blood cell does not. (d) neurons and white blood cells are differentiated cells and thus no longer need to transcribe and translate genes.

8-41 In principle, how many different cell types can an organism having four different types of transcription regulator and thousands of genes create? (a) up to 4 (b) up to 8 (c) up to 16 (d) thousands

Which of the following statements about the globin gene family is true? (a) The globin protein which can carry oxygen molecules throughout an organisms body was first seen in ancient vertebrae species about 500 million years ago (b) The gene duplication that led to the expansions of the globin gene family led to the separation of globin (c) Some of the duplicated globin genes that arose during vertebrate evolution acquired inactivating mutations and become pseudogenes in modern vertebrates (d) As globin gene family members diverged over the course of evolution, all the DNA sequence variations that have accumulated between family members are within the regulatory DNA sequences that affect when and how strongly each globin gene is expressed.

(c)

8-48 The MyoD transcriptional regulator is normally found in differentiating muscle cells and participates in the transcription of genes that produce muscle-specific proteins, such as those needed in contractile tissue. Amazingly, expression of MyoD in fibroblasts causes these cells derived from skin connective tissue to produce proteins normally only seen in muscles. However, some other cell types do not transcribe muscle-specific genes when MyoD is expressed in them. Which of the following statements below is the best explanation of why MyoD can cause fibroblasts to express muscle- specific genes? (a) Unlike some other cell types, fibroblasts have not lost the muscle-specific genes from their genome. (b) The muscle-specific genes must be in heterochromatin in fibroblasts. (c) During their developmental history, fibroblasts have accumulated some transcriptional regulators in common with differentiating muscle cells. (d) The presence of MyoD is sufficient to activate the transcription of muscle- specific genes in all cell types.

(c) During their developmental history, fibroblasts have accumulated some transcriptional regulators in common with differentiating muscle cells.

8-40 Which of the following statements about nucleosomes is true? (a) Nucleosomes activate transcription when bound to the promoter. (b) Although RNA polymerase can access DNA packed within nucleosomes, the general transcription factors and transcriptional regulators cannot. (c) Histone acetyltransferases affect transcription by both altering chromatin structure to allow accessibility to the DNA and by adding acetyl groups to histones that can bind proteins that promote transcription. (d) Histone deacetylases remove lysines from histone tails.

(c) Histone acetyltransferases affect transcription by both altering chromatin structure to allow accessibility to the DNA and by adding acetyl groups to histones that can bind proteins that promote transcription.

8-57 Which of the following is not involved in post-transcriptional control? (a) the spliceosome (b) Dicer (c) Mediator (d) RISC

7-61 Which of the following statements about the proteasome is false? (a) Ubiquitin is a small protein that is covalently attached to proteins to mark them for delivery to the proteasome. (b) Proteases reside in the central cylinder of a proteasome. (c) Misfolded proteins are delivered to the proteasome, where they are sequestered from the cytoplasm and can attempt to refold. (d) The protein stoppers that surround the central cylinder of the proteasome use the energy from ATP hydrolysis to move proteins into the proteasome inner chamber;

(c) Misfolded proteins are delivered to the proteasome, where they are sequestered from the cytoplasm and can attempt to refold.

7-62 Which of the following molecules is thought to have arisen first during evolution? (a) protein (b) DNA (c) RNA (d) all came to be at the same time

Which protein is not encoded in the HIV genome? (a) reverse transcriptase (b) envelope protein (c) RNA polymerase (d) capsid protein

7-64 Ribozymes catalyze which of the following reactions? (a) DNA synthesis (b) transcription (c) RNA splicing (d) protein hydrolysis

Given this information, which of the following is false? (a) These are all highly related species because the sequence divergence between the most divergent species is 3% (b) Species M is just as related to species G as it is to species J (c) Species N is more closely related to the last common ancestor of all these species than to any of the other species shown in the diagram (d) Species G and H are as closely relateed to each other as species J and K are to each other

(c) Species N is more closely related to the last common ancestor of all these species than to any of species in the diagram

7-50 The ribosome is important for catalyzing the formation of peptide bonds. Which of the following statements is true? (a) The number of rRNA molecules that make up a ribosome greatly exceeds the number of protein molecules found in the ribosome. (b) The large subunit of the ribosome is important for binding to the mRNA. (c) The catalytic site for peptide bond formation is formed primarily from an rRNA. (d) Once the large and small subunits of the ribosome assemble, they will not separate from each other until degraded by the proteasome.

Which of these statements is consistent with these sequence-comparison data? (a) The gorilla sequence is more similar to the chimp sequence than to the human sequence (b) since these sequences are so similar this protein must also be found in invertebrates (c) The chimp DNA sequence has likely diverged at the DNA coding for amino acid 15 from the sequence found in the last common ancestor of humans and chimps (d) The last common ancestor of chimps and gorillas most likely used AAA to code for the amino acid number 3

(c) The chimp DNA sequence has likely diverged at the DNA coding for amino acid 15 from the sequence found in the last common ancestor of humans and chimps

7-14 Which one of the following is the main reason that a typical eukaryotic gene is able to respond to a far greater variety of regulatory signals than a typical prokaryotic gene or operon? (a) Eukaryotes have three types of RNA polymerase. (b) Eukaryotic RNA polymerases require general transcription factors. (c) The transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter. (d) Prokaryotic genes are packaged into nucleosomes.

What is the most likely explanation of why the overall mutation rates in bacteria and in humans are roughly similar? (a) Cell division needs to be fast (b) Most mutations are silent (c) There is a narrow range of mutation rates that offers an optimal balance between keeping the genome stable and generating sufficient diversity in a population (d) It benefits multicellular organisms to have some variability among its cells

(c) There is a narrow range of mutation rates that offers an optimal balance between keeping the genome stable and generating sufficient diversity in a population

8-46 Which of the following statements about how fruit flies can develop an eye in the middle of a leg is true? (a) When the Ey gene is expressed in adult leg cells, these cells de- differentiate and become eye cells. (b) The Ey gene encodes a transcription regulator that is the only transcription regulator used to produce a fruit-fly eye. (c) When the Ey gene is introduced into cells that would normally give rise to a leg, the transcription regulators used to control its expression in the leg are different from those that are normally used to control Ey expression in the eye. (d) All the eye cells found in the adult leg are a single cell type and have identical characteristics.

(c) When the Ey gene is introduced into cells that would normally give rise to a leg, the transcription regulators used to control its expression in the leg are different from those that are normally used to control Ey expression in the eye.

8-3 The human genome encodes about 21,000 protein-coding genes. Approximately how many such genes does the typical differentiated human cell express at any one time? (a) 21,000—all of them (b) between 18,900 and 21,000—at least 90% of the genes (c) between 5000 and 15,000 (d) less than 2100

8-11 Operons ___________________________. (a) are commonly found in eukaryotic cells. (b) are transcribed by RNA polymerase II. (c) contain a cluster of genes transcribed as a single mRNA. (d) can only be regulated by gene activator proteins.

7-4 RNA in cells differs from DNA in that ___________________. (a) it contains the base uracil, which pairs with cytosine. (b) it is single-stranded and cannot form base pairs. (c) it is single-stranded and can fold up into a variety of structures. (d) the sugar ribose contains fewer oxygen atoms than does deoxyribose.

8-61 Which (a) One miRNA can regulate the expression of many genes. (b) miRNAs are transcribed in the nucleus from genomic DNA. (c) miRNAs are produced from rRNAs. (d) miRNAs are made by RNA polymerase. of the following statements about miRNAs is false

Alternative exons can arise through the duplication and divergence of existing exons. What type of mutation below would be least tolerated during the evolution of a new exon? (a) a nucleotide change of A to G (b) a deletion of three consective bases (c) mutation of the first nucleotide in the intron

7-51 Which of the following statements is true? (a) Ribosomes are large RNA structures composed solely of rRNA. (b) Ribosomes are synthesized entirely in the cytoplasm. (c) rRNA contains the catalytic activity that joins amino acids together. (d) A ribosome binds one tRNA at a time.

7-22 The sigma subunit of bacterial RNA polymerase ___________________. (a) contains the catalytic activity of the polymerase. (b) remains part of the polymerase throughout transcription. (c) recognizes promoter sites in the DNA. (d) recognizes transcription termination sites in the DNA.

8-8 Which of these method(s) of controlling eukaryotic gene expression is NOT employed in prokaryotic cells? A. controlling how often a gene is transcribed B. controlling how an RNA transcript is spliced C. controlling which mRNAs are exported from the nucleus to the cytosol D. controlling which mRNAs are translated into protein by the ribosomes E. controlling how rapidly proteins are destroyed once they are made

B. controlling how an RNA transcript is spliced C. controlling which mRNAs are exported from the nucleus to the cytosol

5-14 Which of the following structural characteristics is not normally observed in a DNA duplex? (a) purine-pyrimidine pairs (b) external sugar-phosphate backbone (c) uniform left-handed twist (d) antiparallel strands

5-18 Which DNA base pair is represented in Figure Q5-18? (a) A-T (b) T-A (c) G-C (d) C-G

5-36 What type of macromolecule helps package DNA in eukaryotic chromosomes? (a) lipids (b) carbohydrates (c) proteins (d) RNA

5-38 The process of sorting human chromosome pairs by size and morphology is called karyotyping. A modern method employed for karyotyping is called chromosome painting. How are individual chromosomes "painted"? (a) with a laser (b) using fluorescent antibodies (c) using fluorescent DNA molecules (d) using green fluorescent protein

5-52 Nucleosomes are formed when DNA wraps _____ times around the histone octamer in a ______ coil. (a) 2.0, right-handed (b) 2.5, left-handed (c) 1.7, left-handed (d) 1.3, right-handed

5-55 The core histones are small, basic proteins that have a globular domain at the C-terminus and a long, extended conformation at the N-terminus. Which of the following is not true of the N-terminal "tail" of these histones? (a) It is subject to covalent modifications (b) It extends out of the nucleosome core (c) It binds to DNA in a sequence-specific manner (d) It helps DNA pack tightly

5-59 Although the chromatin structure of interphase and mitotic chromosomes is very compact, DNA-binding proteins and protein complexes must be able to gain access to the DNA molecule. Chromatin-remodeling complexes provide this access by __________________. (a) recruiting other enzymes (b) modifying the N-terminal tails of core histones (c) using the energy of ATP hydrolysis to move nucleosomes (d) denaturing the DNA by interfering with hydrogen-bonding between base pairs

5-6 You are a virologist interested in studying the evolution of viral genomes. You are studying two newly isolated viral strains and have sequenced their genomes. You find that the genome of strain 1 contains 25% A, 55% G, 20% C, and 10% T. You report that you have isolated a virus with a single-stranded DNA genome. Based on what evidence can you make this conclusion? (a) single-stranded genomes always have a large percentage of purines (b) using the formula: G - A = C + T (c) Double-stranded genomes have equal amounts of A and T (d) Single-stranded genomes have a higher rate of mutation

5-63 When there is a well-established segment of heterochromatin on an interphase chromosome, there is usually a special barrier sequence that prevents the heterochromatin from expanding along the entire chromosome. Gene A, which is normally expressed, has been moved by DNA recombination near an area of heterochromatin. None of the daughter cells produced after this recombination event express gene A, even though its DNA sequence is unchanged. What is the best way to describe what has happened to the function of gene A in these cells? (a) barrier destruction (b) heterochromatization (c) epigenetic inheritance (d) euchromatin depletion

5-66 How do changes in histone modifications lead to changes in chromatin structure? (a) They directly lead to changes in the positions of the core histones (b) They change the affinity between the histone octamer and the DNA (c) They help recruit other proteins to the chromatin (d) They cause the histone N-terminal tails to become hyperextended

Beside the distortion in the DNA backbone caused by a mismatched base pair, what additional mark is there on eukaryotic DNA to indicate which strand needs to be repaired? (a) a nick in the template strand (b) a chemical modification of the new strand (c) a nick in the new strand (d) a sequence gap in the new strand

DNA replication is considered semiconservative because ____________________________. (a) after many rounds of DNA replication, the original DNA double helix is still intact. (b) each daughter DNA molecule consists of two new strands copied from the parent DNA molecule. (c) each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand. (d) new DNA strands must be copied from a DNA template.

In addition to the repair of DNA double-strand breaks, homologous recombination is a mechanism for generating genetic diversity by swapping segments of parental chromosomes. During which process does swapping occur? (a) DNA replication (b) DNA repair (c) meiosis (d) transposition

Select the option that best completes the following statement: Nonhomologous end joining is a process by which a double-stranded DNA end is joined ___________________. (a) to a similar stretch of sequence on the complementary chromosome. (b) after repairing any mismatches. (c) to the nearest available double-stranded DNA end. (d) after filling in any lost nucleotides, helping to maintain the integrity of the DNA sequence.

Several members of the same family were diagnosed with the same kind of cancer when they were unusually young. Which one of the following is the most likely explanation for this phenomenon? It is possible that the individuals with the cancer have _______________________. (a) inherited a cancer-causing gene that suffered a mutation in an ancestor's somatic cells. (b) inherited a mutation in a gene required for DNA synthesis. (c) inherited a mutation in a gene required for mismatch repair. (d) inherited a mutation in a gene required for the synthesis of purine nucleotides.

Sometimes, chemical damage to DNA can occur just before DNA replication begins, not giving the repair system enough time to correct the error before the DNA is duplicated. This gives rise to mutation. If the adenosine in the sequence TCAT is depurinated and not repaired, which of the following is the point mutation you would observe after this segment has undergone two rounds of DNA replication? (a) TCGT (b) TAT (c) TCT (d) TGTT

The chromatin structure in eukaryotic cells is much more complicated than that observed in prokaryotic cells. This is thought to be the reason that DNA replication occurs much faster in prokaryotes. How much faster is it? (a) 2× (b) 5× (c) 10× (d) 100×

The process of DNA replication requires that each of the parental DNA strands be used as a ___________________ to produce a duplicate of the opposing strand. (a) catalyst (b) competitor (c) template (d) copy

Will panels C and D be faithfully transmitted during cell division?

C will be segregated to progeny properly D will not be because one product has 2 centromeres that will cause severe damage to it during mitosis and the other product does not have one at all and will cause the chromosome to be rapidly lost

5-41 Which of the following questions would not be answered by using karyotyping? (a) Is the individual genetically female or male? (b) Do any of the chromosomes contain pieces that belong to other chromosomes? (c) Does the individual have an extra chromosome? (d) Do any chromosomes contain point mutations?

5-5 In a DNA double helix, _____________________. (a) the two DNA strands are identical. (b) purines pair with purines. (c) thymine pairs with cytosine. (d) the two DNA strands run antiparallel.

5-54 The octameric histone core is composed of four different histone proteins, assembled in a stepwise manner. Once the core octamer has been formed, DNA wraps around it to form a nucleosome core particle. Which of the following histone proteins does not form part of the octameric core? (a) H4 (b) H2A (c) H3 (d) H1

5-69 The inactivation of one X chromosome is established by the directed spreading of heterochromatin. The silent state of this chromosome is _______________ in the subsequent cell divisions. (a) completed (b) switched (c) erased (d) maintained

5-9 Several experiments were required to demonstrate how traits are inherited. Which scientist or team of scientists obtained definitive results demonstrating that DNA is the genetic molecule? (a) Griffith (b) Watson (c) Crick (d) Hershey and Chase

A molecule of bacterial DNA introduced into a yeast cell is imported into the nucleus but fails to replicate with the yeast DNA. Where do you think the block to replication arises? Choose the protein or protein complex below that is most probably responsible for the failure to replicate bacterial DNA. Give an explanation for your answer. (a) primase (b) helicase (c) DNA polymerase (d) initiator proteins

Even though DNA polymerase has a proofreading function, it still introduces errors in the newly synthesized strand at a rate of 1 per 107 nucleotides. To what degree does the mismatch repair system decrease the error rate arising from DNA replication? (a) 2-fold (b) 5-fold (c) 10-fold (d) 100-fold

How does the total number of replication origins in bacterial cells compare with the number of origins in human cells? (a) 1 versus 100 (b) 5 versus 500 (c) 10 versus 1000 (d) 1 versus 10,000

Human beings with the inherited disease xeroderma pigmentosum have serious problems with lesions on their skin and often develop skin cancer with repeated exposure to sunlight. What type of DNA damage is not being recognized in the cells of these individuals? (a) chemical damage (b) X-ray irradiation damage (c) mismatched bases (d) ultraviolet irradiation damage

If the genome of the bacterium E. coli requires about 20 minutes to replicate itself, how can the genome of the fruit fly Drosophila be replicated in only 3 minutes? (a) The Drosophila genome is smaller than the E. coli genome. (b) Eukaryotic DNA polymerase synthesizes DNA at a much faster rate than prokaryotic DNA polymerase. (c) The nuclear membrane keeps the Drosophila DNA concentrated in one place in the cell, which increases the rate of polymerization. (d) Drosophila DNA contains more origins of replication than E. coli DNA.

Telomeres serve as caps at the ends of linear chromosomes. Which of the following is not true regarding the replication of telomeric sequences? (a) The lagging-strand telomeres are not completely replicated by DNA polymerase. (b) Telomeres are made of repeating sequences. (c) Additional repeated sequences are added to the template strand. (d) The leading strand doubles back on itself to form a primer for the lagging strand.

The events listed below are all necessary for homologous recombination to occur properly: A. Holliday junction cut and ligated B. strand invasion C. DNA synthesis D. DNA ligation E. double-strand break F. nucleases create uneven strands Which of the following is the correct order of events during homologous recombination? (a) E, B, F, D, C, A (b) B, E, F, D, C, A (c) C, E, F, B, D, A (d) E, F, B, C, D, A

What part of the DNA replication process would be most directly affected if a strain of bacteria lacking DNA ligase were used to make the cell extracts? (a) initiation of DNA synthesis (b) Okazaki fragment synthesis (c) leading-strand elongation (d) lagging-strand completion

What part of the DNA replication process would be most directly affected if a strain of bacteria lacking the exonuclease activity of DNA polymerase were used to make the cell extracts? (a) initiation of DNA synthesis (b) Okazaki fragment synthesis (c) leading-strand elongation (d) lagging-strand completion

Which of the following statements about the newly synthesized strand of a human chromosome is true? (a) It was synthesized from a single origin solely by continuous DNA synthesis. (b) It was synthesized from a single origin by a mixture of continuous and discontinuous DNA synthesis. (c) It was synthesized from multiple origins solely by discontinuous DNA synthesis. (d) It was synthesized from multiple origins by a mixture of continuous and discontinuous DNA synthesis.

Which of the following statements correctly explains what it means for DNA replication to be bidirectional? (a) The replication fork can open or close, depending on the conditions. (b) The DNA replication machinery can move in either direction on the template strand. (c) Replication-fork movement can switch directions when the fork converges on another replication fork. (d) The replication forks formed at the origin move in opposite directions.

You are examining the DNA sequences that code for the enzyme phosphofructokinase in skinks and Komodo dragons. You notice that the coding sequence that actually directs the sequence of amino acids in the enzyme is very similar in the two organisms but that the surrounding sequences vary quite a bit. What is the most likely explanation for this? (a) Coding sequences are repaired more efficiently. (b) Coding sequences are replicated more accurately. (c) Coding sequences are packaged more tightly in the chromosomes to protect them from DNA damage. (d) Mutations in coding sequences are more likely to be deleterious to the organism than mutations in noncoding sequences.

You have discovered an "Exo-" mutant form of DNA polymerase in which the 3′- to-5′ exonuclease function has been destroyed but the ability to join nucleotides together is unchanged. Which of the following properties do you expect the mutant polymerase to have? (a) It will polymerize in both the 5′-to-3′ direction and the 3′-to-5′ direction. (b) It will polymerize more slowly than the normal Exo+ polymerase. (c) It will fall off the template more frequently than the normal Exo+ polymerase. (d) It will be more likely to generate mismatched base pairs.

Describe a mechanism that might drive evolution toward more or larger introns and could account for the introns late hypothesis.

Exon shuffling and acquisition of intron sequences as binding sites for crossovers

True or False Nearly every instance of DNA duplication leads to a newly functional gene

False

True or false? To meet a challenge or develop a new function, evolution essentially builds from first principles designing from scratch to find the best possible solution

False

T or F? Introns and transposons tend to slow the evolution of new genes.

False they can act as sites where recombinational crossovers occur and transposons also catalyze genetic rearrangements

T or F? All highly conserved stretches of DNA in the genome are transcribed into RNA.

False, many are not transcribed and contain information for regulation of gene expression

Mobile genetic elements are sometimes called "jumping genes" because they move from place to place throughout the genome. The exact mechanism by which they achieve this mobility depends on the genes contained within the mobile element. Which of the following mobile genetic elements carries both a transposase and a reverse transcriptase gene?

5-10 Fred Griffith studied two strains of Streptococcus pneumonia, one that causes a lethal infection when injected into mice, and a second that is harmless. He observed that pathogenic bacteria that have been killed by heating can no longer cause an infection. But when these heat-killed bacteria are mixed with live, harmless bacteria, this mixture is capable of infecting and killing a mouse. What did Griffith conclude from this experiment? (a) The infectious strain cannot killed by heating (b) The heat-killed pathogenic bacteria "transformed" the harmless strain into a lethal one (c) The harmless strain somehow revived the heat-killed pathogenic bacteria (d) The mice had lost their immunity to infection with S. pneumoniae

5-25 The manner in which a gene sequence is related to its respective protein sequence is referred to as the _________ code. (a) protein (b) genetic (c) translational (d) expression

5-26 The information stored in the DNA sequences is used directly as a template to make ___________. (a) lipids (b) RNA (c) polypeptides (d) carbohydrates

5-3 Mitotic chromosomes were first visualized with the use of very simple tools: a basic light microscope and some dyes. Which of the following characteristics of mitotic chromosomes reflects how they were named? (a) motion (b) color (c) shape (d) location

5-35 The human genome is a diploid genome. However, when germ-line cells produce gametes, these specialized cells are haploid. What is the total number of chromosomes found in each of the gametes (egg or sperm) in your body? (a) 22 (b) 23 (c) 44 (d) 46

5-45 Figure Q5-45 clearly depicts the nucleolus, a nuclear structure that looks like a large, dark region when stained. The other dark, speckled regions in this image are the locations of particularly compact chromosomal segments called ____________. (a) euchromatin (b) heterochromatin (c) nuclear pores (d) nucleosomes

5-48 Interphase chromosomes are about______ times less compact than mitotic chromosomes, but still are about______ times more compact than a DNA molecule in its extended form. a) 10, 1000 (b) 20, 500 (c) 5, 2000 (d) 50, 200

5-56 Stepwise condensation of linear DNA happens in five different packing processes. Which of the following four processes has a direct requirement for histone H1? (a) formation of "beads-on-a-string" (b) formation of the 30-nm fiber (c) looping of the 30-nm fiber (d) packing of loops to form interphase chromosomes

5-61 The N-terminal tail of histone H3 can be extensively modified, and depending on the number, location, and combination of these modifications, these changes may promote the formation of heterochromatin. What is the result of heterochromatin formation? (a) increase in gene expression (b) gene silencing (c) recruitment of remodeling complexes (d) displacement of histone H1

5-65 Which of the following is not a chemical modification commonly found on core histone N-terminal tails? (a) methylation (b) hydroxylation (c) phosphorylation (d) acetylation

5-67 Most eukaryotic cells only express 20-30% of the genes they possess. The formation of heterochromatin maintains the other genes in a transcriptionally silent (unexpressed) state. Which histone modification directs the formation of the most common type of heterochromatin? (a) H3 lysine 4 methylation (b) H3 lysine 9 methylation (c) H3 lysine 14 methylation (d) H3 lysine 27 methylation

DNA polymerases are processive, which means that they remain tightly associated with the template strand while moving rapidly and adding nucleotides to the growing daughter strand. Which piece of the replication machinery accounts for this characteristic? (a) helicase (b) sliding clamp (c) single-strand binding protein (d) primase

Homologous recombination is an important mechanism in which organisms use a "backup" copy of the DNA as a template to fix double-strand breaks without loss of genetic information. Which of the following is not necessary for homologous recombination to occur? (a) 3′ DNA strand overhangs (b) 5′ DNA strand overhangs (c) a long stretch of sequence similarity (d) nucleases

How many replication forks are formed when an origin of replication is opened? (a) 1 (b) 2 (c) 3 (d) 4

In somatic cells, if a base is mismatched in one new daughter strand during DNA replication, and is not repaired, what fraction of the DNA duplexes will have a permanent change in the DNA sequence after the second round of DNA replication? (a) 1/2 (b) 1/4 (c) 1/8 (d) 1/16

Initiator proteins bind to replication origins and disrupt hydrogen bonds between the two DNA strands being copied. Which of the factors below does not contribute to the relative ease of strand separation by initiator proteins? (a) replication origins are rich in A-T base pairs (b) the reaction can occur at room temperature (c) they only separate a few base pairs at a time (d) once opened, other proteins of the DNA replication machinery bind to the origin

Sickle-cell anemia is an example of an inherited disease. Individuals with this disorder have misshapen (sickle-shaped) red blood cells caused by a change in the sequence of the β-globin gene. What is the nature of the change? (a) chromosome loss (b) base-pair change (c) gene duplication (d) base-pair insertion

The DNA duplex consists of two long covalent polymers wrapped around each other many times over their entire length. The separation of the DNA strands for replication causes the strands to be "overwound" in front of the replication fork. How does the cell relieve the torsional stress created along the DNA duplex during replication? (a) Nothing needs to be done because the two strands will be separated after replication is complete. (b) Topoisomerases break the covalent bonds of the backbone allowing the local unwinding of DNA ahead of the replication fork. (c) Helicase unwinds the DNA and rewinds it after replication is complete. (d) DNA repair enzymes remove torsional stress as they replace incorrectly paired bases.

The classic experiments conducted by Meselson and Stahl demonstrated that DNA replication is accomplished by employing a ________________ mechanism. (a) continuous (b) semiconservative (c) dispersive (d) conservative

What part of the DNA replication process would be most directly affected if a strain of bacteria lacking single-strand binding protein were used to make the cell extracts? (a) initiation of DNA synthesis (b) Okazaki fragment synthesis (c) leading-strand elongation (d) lagging-strand completion

Which of the following statements about sequence proofreading during DNA replication is false? (a) The exonuclease activity is in a different domain of the DNA polymerase. (b) The exonuclease activity cleaves DNA in the 5′-to-3′ direction. (c) The DNA proofreading activity occurs concomitantly with strand elongation. (d) If an incorrect base is added, it is "unpaired" before removal.

Which of the following statements is not an accurate statement about thymine dimers? (a) Thymine dimers can cause the DNA replication machinery to stall. (b) Thymine dimers are covalent links between thymidines on opposite DNA strands. (c) Prolonged exposure to sunlight causes thymine dimers to form. (d) Repair proteins recognize thymine dimers as a distortion in the DNA backbone.

T or F? Most mutation and genome alterations have neutral consequences

True

T or F? Proteins required for growth, metabolism, and cell division are more highly conserved than those involved in development and in response to the environment.

True

TorF? To find functionally important regions of the genome, it is more useful to compare species whose last common ancestor lived 100 million years go rather than 5 million years ago

True

A covalent bond between two atoms is formed as a result of the ______________. (a) sharing of electrons. (b) loss of electrons from both atoms. (c) loss of a proton from one atom. (d) transfer of electrons from one atom to the other.

Although covalent bonds are 10-100 times stronger than noncovalent interactions, many biological processes depend upon the number and type of noncovalent interactions between molecules. Which of the noncovalent interactions below will contribute most to the strong and speciﬁc binding of two molecules, such as a pair of proteins? (a) electrostatic attractions (b) hydrogen bonds (c) hydrophobic interactions (d) Van der Waals attractions

Aromatic carbon compounds such as benzene are planar and very stable. Double-bond character extends around the entire ring, which is why it is often drawn as a hexagon with a circle inside. This characteristic is caused by electron __________. (a) resonance. (b) pairing. (c) partial charge. (d) stacking

By definition, prokaryotic cells do not possess __________. (a) a nucleus. (b) replication machinery. (c) ribosomes. (d) membrane bilayers.

Cyclic AMP (cAMP) is a small molecule that associates with its binding site with a high degree of speciﬁcity. Which types of noncovalent interactions are the most important for providing the "hand in a glove" binding of cAMP? (a) hydrogen bonds (b) electrostatic interactions (c) van der Waals interactions (d) hydrophobic interactions

Drosophila melanogaster is a/an __________. This type of animal is the most abundant of all animal species, making it an appropriate choice as an experimental model. (a) insect (b) bird (c) amphibian (d) mammal

During respiration, energy is retrieved from the high-energy bonds found in certain organic molecules. Which of the following, in addition to energy, are the ultimate products of respiration? (a) CO2, H2O (b) CH3, H2O (c) CH2OH, O2 (d) CO2, O2

Each nucleotide in DNA and RNA has an aromatic base. What is the principal force that keeps the bases in a polymer from interacting with water? (a) hydrophobic interactions (b) hydrogen bonds (c) covalent bonds (d) van der Waals interactions

Eukaryotic cells are able to trigger the release of material from secretory vesicles to the extracellular space using a process called exocytosis. An example of materials commonly released this way is _____________. (a) hormones. (b) nucleic acids. (c) sugars. (d) cytosolic proteins.

For some proteins, small molecules are integral to their structure and function. Enzymes can synthesize some of these small molecules, whereas others, called vitamins, must be ingested in the food we eat. Which of the following molecules is not classiﬁed as a vitamin but does require the ingestion of a vitamin for its production? (a) retinal (b) biotin (c) zinc (d) heme

For the reaction Y◊X at standard conditions with [Y] = 1 M and [X] = 1 M, ΔG is initially a large negative number. As the reaction proceeds, [Y] decreases and [X] increases until the system reaches equilibrium. How do the values of ΔG and ΔG° change as the reaction equilibrates? (a) ΔG becomes less negative and ΔG° stays the same. (b) ΔG becomes positive and ΔG° becomes positive. (c) ΔG stays the same and ΔG° becomes less negative. (d) ΔG reaches zero and ΔG° becomes more negative.

Globular proteins fold up into compact, spherical structures that have uneven surfaces. They tend to form multisubunit complexes, which also have a rounded shape. Fibrous proteins, in contrast, span relatively large distances within the cell and in the extracellular space. Which of the proteins below is not classiﬁed as a ﬁbrous protein? (a) elastase (b) collagen (c) keratin (d) elastin

Instead of studying one or two proteins or protein complexes present in the cell at any given time, we can now look at a snapshot of all proteins being expressed in cells being grown in speciﬁc conditions. This large-scale, systematic approach to the study of proteins is called _______________. (a) proteomics. (b) structural biology. (c) systems biology. (d) genomics

Isomerization of glucose 1-phosphate to glucose 6-phosphate is energetically favorable. At 37°C, ΔG° = -1.42 log10K. What is the equilibrium constant for this reaction if ΔG° = -1.74 kcal/mole at 37°C? (a) 16.98 (b) 0.09 (c) -0.09 (d) 0.39

Many of the mechanisms that cells use for maintenance and reproduction were first studied at the molecular level in bacteria. Which bacterial species had a central role in advancing the field of molecular biology? (a) E. coli (b) D. melanogaster (c) S. pombe (d) C. elegans

Oxidation is a favorable process in an aerobic environment, which is the reason cells are able to derive energy from the oxidation of macromolecules. Once carbon has been oxidized to _______________, its most stable form, it can only cycle back into the organic portion of the carbon cycle through __________________. (a) CO2, photosynthesis. (b) CH3, combustion. (c) CO2, respiration. (d) CO, reduction.

Polypeptides are synthesized from amino acid building blocks. The condensation reaction between the growing polypeptide chain and the next amino acid to be added involves the loss of ________________. (a) a water molecule. (b) an amino group. (c) a carbon atom. (d) a carboxylic acid group.

Protein folding can be studied using a solution of puriﬁed protein and a denaturant (urea), a solvent that interferes with noncovalent interactions. Which of the following is observed after the denaturant is removed from the protein solution? (a) The polypeptide returns to its original conformation. (b) The polypeptide remains denatured. (c) The polypeptide forms solid aggregates and precipitates out of solution. (d) The polypeptide adopts a new, stable conformation.

Proteins can assemble to form large complexes that work coordinately, like moving parts inside a single machine. Which of the following steps in modulating the activity of a complex protein machine is least likely to be directly affected by ATP or GTP hydrolysis? (a) translation of protein components (b) conformational change of protein components (c) complex assembly (d) complex disassembly

Select the option that best finishes the following statement: "Evolution is a process __________." (a) that can be understood based on the principles of mutation and selection. (b) that results from repeated cycles of adaptation over billions of years. (c) by which all present-day cells arose from 4-5 different ancestral cells. (d) that requires hundreds of thousands of years.

The flow of genetic information is controlled by a series of biochemical reactions that result in the production of proteins, each with its own specific order of amino acids. Choose the correct series of biochemical reactions from the options presented here. (a) replication, transcription, translation (b) replication, translation, transcription (c) translation, transcription, replication (d) translation, replication, transcription

The mitochondrial proteins found in the inner membrane are involved in the conversion of ADP to ATP, a source of energy for the cell. This process consumes which of the following substances? (a) oxygen (b) nitrogen (c) sulfur (d) carbon dioxide

The net distance a molecule travels through the cytosol via diffusion is relatively short in comparison with the total distance it may need to travel. This is because movement governed by diffusion alone is a ________________ process that is most effective for the dispersion of small molecules over short distances. (a) slow (b) random (c) regulated (d) complicated

The process of generating monoclonal antibodies is labor-intensive and expensive. An alternative is to use polyclonal antibodies. A subpopulation of puriﬁed polyclonal antibodies that recognize a particular antigen can be isolated by chromatography. Which type of chromatography is used for this purpose? (a) afﬁnity (b) ion-exchange (c) gel-ﬁltration (d) any of the above

The study of enzymes also includes an examination of how the activity is regulated. Molecules that can act as competitive inhibitors for a speciﬁc reaction are often similar in shape and size to the enzyme's substrate. Which variable(s) used to describe enzyme activity will remain the same in the presence and absence of a competitive inhibitor? (a) Vmax (b) V (c) Vmax and Km (d) Km

The three-dimensional coordinates of atoms within a folded protein are determined experimentally. After researchers obtain a protein's structural details, they can use different techniques to highlight particular aspects of the structure. What visual model best displays a protein's secondary structures (α helices and β sheets)? (a) ribbon (b) space-ﬁlling (c) backbone (d) wire

There are 20^100 different possible sequence combinations for a protein chain with 100 amino acids. In addition to the amino acid sequence of the protein, what other factors increase the potential for diversity in these macromolecules? (a) free rotation around single bonds during synthesis (b) noncovalent interactions sampled as protein folds (c) the directionality of amino acids being added (d) the planar nature of the peptide bond

What information regarding an enzyme-catalyzed reaction is obtained in a plot of the inverse of the initial velocities against the inverse of the corresponding substrate concentrations? (a) 1/Vmax and 1/Km (b) 1/V and 1/[S] (c) Vmax and Km (d) V and [S]

Which of the following are examples of isomers? (a) glucose and galactose (b) alanine and glycine (c) adenine and guanine (d) glycogen and cellulose

Which of the following elements is least abundant in living organisms? (a) sulfur (b) carbon (c) oxygen (d) nitrogen

Which of the following expressions accurately describes the calculation of pH? (a) pH = -log10[H+]+ (b) pH = log10[H] (c) pH = -log2[H+] (d) pH = -log10[OH-]

Which of the following factors do not inﬂuence the length of a covalent bond? (a) the tendency of atoms to ﬁll the outer electron shells (b) the attractive forces between negatively charged electrons and positively charged nuclei (c) the repulsive forces between the positively charged nuclei (d) the minimization of repulsive forces between the two nuclei by the cloud of shared electrons

Which of the following globular proteins is used to form ﬁlaments as an intermediate step to assembly into hollow tubes? (a) tubulin (b) actin (c) keratin (d) collagen

Which of the following is not a feature commonly observed in α helices? (a) left-handedness (b) one helical turn every 3.6 amino acids (c) cylindrical shape (d) amino acid side chains that point outward

Which of the following methods would be the most suitable to assess whether your protein exists as a monomer or in a complex? (a) gel-ﬁltration chromatography (b) gel electrophoresis (c) western blot analysis (d) ion-exchange chromatography

Which of the following statements about allostery is true? (a) of in the same Allosteric regulators are often products other chemical reactions biochemical pathway. (b) Allosteric regulation is always used for negative regulation of enzyme activity. (c) Enzymes are the only types of proteins that are subject to allosteric regulation. (d) Binding of allosteric molecules usually locks an enzyme in its current conformation, such that the enzyme cannot adopt a different conformation.

Which subatomic particles contribute to the atomic number for any given element? (a) protons (b) protons and neutrons (c) neutrons (d) protons and electrons

You have two puriﬁed samples of protein Y: the wild-type (nonmutated) protein and a mutant version with a single amino acid substitution. When washed through the same gel- ﬁltration column, mutant protein Y runs through the column more slowly than the normal protein. Which of the following changes in the mutant protein is most likely to explain this result? (a) the loss of a binding site on the mutant-protein surface through which protein Y normally forms dimers (b) a change that results in the mutant protein acquiring an overall positive instead of a negative charge (c) a change that results in the mutant protein being larger than the wild-type protein (d) a change that results in the mutant protein having a slightly different shape from the wild-type protein

In the ﬁrst stage of photosynthesis, light energy is converted into what other form of energy? (a) electrical (b) chemical (c) potential (d) kinetic

a or d

The number of distinct protein species found in humans and other organisms can vastly succeed the number of genes. This is largely due to ______________ ______________.

alternative splicing

A. thaliana, or Arabidopsis, is a common weed. Biologists have selected it over hundreds of thousands of other flowering plant species to serve as an experimental model organism because __________________. (a) it can withstand extremely cold climates. (b) it can reproduce in 8-10 weeks. (c) it produces thousands of offspring per plant. (d) Both (b) and (c) are true.

Because there are four different monomer building blocks that can be used to assemble RNA polymers, the number of possible sequence combinations that can be created for an RNA molecule made of 100 nucleotides is _______. (a) 100 (b) 4^100 (c) 4 × 100 (d) 100/4

Both DNA and RNA are synthesized by covalently linking a nucleoside triphosphate to the previous nucleotide, constantly adding to a growing chain. In the case of DNA, the new strand becomes part of a stable helix. The two strands are complementary in sequence and antiparallel in directionality. What is the principal force that holds these two strands together? (a) ionic interactions (b) hydrogen bonds (c) covalent bonds (d) van der Waals interactions

Brewer's yeast, apart from being an irreplaceable asset in the brewery and in the bakery, is an experimental organism used to study eukaryotic cells. However, it does have some limitations. Which of the processes below cannot be studied in yeast? (a) DNA replication (b) cell motility (c) exocytosis (d) cell division

Caenorhabditis elegans is a nematode. During its development, it produces more than 1000 cells. However, the adult worm has only 959 somatic cells. The process by which 131 cells are specifically targeted for destruction is called ______________. (a) directed cell pruning. (b) programmed cell death. (c) autophagy. (d) necrosis.

Carbon 14 is an unstable isotope of carbon that decays very slowly. Compared to the common, stable carbon 12 isotope, carbon 14 has two additional ______________. (a) electrons. (b) neutrons. (c) protons. (d) ions.

Catalysts are molecules that lower the activation energy for a given reaction. Cells produce their own catalysts called _____________. (a) proteins. (b) enzymes. (c) cofactors. (d) complexes.

Changes in DNA sequence from one generation to the next may result in offspring that are altered in fitness compared with their parents. The process of change and selection over the course of many generations is the basis of __________. (a) mutation. (b) evolution. (c) heredity. (d) reproduction.

Chemical reactions carried out by living systems depend on the ability of some organisms to capture and use atoms from nonliving sources in the environment. The speciﬁc subset of these reactions that break down nutrients in food can be described as _____________. (a) metabolic. (b) catabolic. (c) anabolic. (d) biosynthetic.

Coiled-coils are typically found in proteins that require an elongated structural framework. Which of the following proteins do you expect to have a coiled-coil domain? (a) insulin (b) collagen (c) myoglobin (d) porin

DNA and RNA are different types of nucleic acid polymer. Which of the following is true of DNA but not true of RNA? (a) It contains uracil. (b) It contains thymine. (c) It is single-stranded. (d) It has 5′-to-3′ directionality.

Living systems are incredibly diverse in size, shape, environment, and behavior. It is estimated that there are between 10 million and 100 million different species. Despite this wide variety of organisms, it remains difficult to define what it means to say something is alive. Which of the following can be described as the smallest living unit? (a) DNA (b) cell (c) organelle (d) protein

Oxidation is the process by which oxygen atoms are added to a target molecule. Generally, the atom that is oxidized will experience which of the following with respect to the electrons in its outer shell? (a) a net gain (b) a net loss (c) no change (d) an equal sharing

Photosynthesis enables plants to capture the energy from sunlight. In this essential process, plants incorporate the carbon from CO 2 into high-energy __________ molecules, which the plant cell mitochondria use to produce ATP. (a) fat (b) sugar (c) protein (d) fiber

Proteins bind selectively to small-molecule targets called ligands. The selection of one ligand out of a mixture of possible ligands depends on the number of weak, noncovalent interactions in the protein's ligand-binding site. Where is the binding site typically located in the protein structure? (a) on the surface of the protein (b) inside a cavity on the protein surface (c) buried in the interior of the protein (d) forms on the surface of the protein in the presence of ligand

Seed oils are often dehydrogenated and added back into processed foods as partly unsaturated fatty acids. In comparison with the original oil, the new fatty acids have additional double carbon-carbon bonds, replacing what were once single bonds. This process could also be described as _____________. (a) isomerization. (b) oxidation. (c) reduction. (d) protonation.

Select the option that correctly finishes the following statement: "A cell's genome _________________." (a) is defined as all the genes being used to make protein. (b) contains all of a cell's DNA. (c) constantly changes, depending upon the cell's environment. (d) is altered during embryonic development.

Studies conducted with a lysozyme mutant that contains an Asp◊Asn change at position 52 and a a in enzymatic Glu◊Gln change at position 35 exhibited almost complete loss activity. What is the most likely explanation for the decrease in enzyme activity in the mutant? (a) increased afﬁnity for substrate (b) absence of negative charges in the active site (c) change in the active-site scaffold (d) larger amino acids in the active site decreases the afﬁnity for substrate

The activity, the phosphorylation of a protein is typically associated with a change in assembly of a protein complex, or the triggering of a downstream signaling cascade. The addition of ubiquitin, a small polypeptide, is another type of covalent modiﬁcation that can affect the protein function. Ubiquitylation often results in ______________. (a) membrane association. (b) protein degradation. (c) protein secretion. (d) nuclear translocation.

The cytoskeleton provides support, structure, motility, and organization, and it forms tracks to direct organelle and vesicle transport. Which of the cytoskeletal elements listed below is the thickest? (a) actin filaments (b) microtubules (c) intermediate filaments (d) none of the above (all the same thickness)

The nucleus, an organelle found in eukaryotic cells, confines the __________, keeping them separated from other components of the cell. (a) lysosomes (b) chromosomes (c) peroxisomes (d) ribosomes

The potential energy stored in high-energy bonds is commonly harnessed when the bonds are split by the addition of _______________ in a process called _____________. (a) ATP, phosphorylation. (b) water, hydrolysis. (c) hydroxide, hydration. (d) acetate, acetylation.

The second law of thermodynamics states that the disorder in any system is always increasing. In simple terms, you can think about dropping NaCl crystals into a glass of water. The solvation and diffusion of ions is favored because there is an increase in _____________. (a) pH. (b) entropy. (c) ions. (d) stored energy.

The variations in the physical characteristics between different proteins are inﬂuenced by the overall amino acid compositions, but even more important is the unique amino acid ______________. (a) number. (b) sequence. (c) bond. (d) orientation.

The ﬁrst task you are assigned in your summer laboratory job is to prepare a concentrated NaOH stock solution. The molecular weight of NaOH is 40. How many grams of solid NaOH will you need to weigh out to obtain a 500 mL solution that has a concentration of 10 M? (a) 800 g (b) 200 g (c) 400 g (d) 160 g

To study how proteins fold, scientists must be able to purify the protein of interest, use solvents to denature the folded protein, and observe the process of refolding at successive time the points. What is the effect of the solvents used in denaturation process? (a) The solvents break all covalent interactions. (b) The solvents break all noncovalent interactions. (c) The solvents break some of the noncovalent interactions, resulting in a misfolded protein. (d) The solvents create a new protein conformation.

Two or three α helices can sometimes wrap around each other to form coiled-coils. The stable wrapping of one helix around another is typically driven by ________________ interactions. (a) hydrophilic (b) hydrophobic (c) van der Waals (d) ionic

What is the smallest distance two points can be separated and still resolved using light microscopy? (a) 20 nm (b) 0.2 μm (c) 2 μm (d) 200 μm

When elemental sodium is added to water, the sodium atoms ionize spontaneously. Uncharged Na becomes Na+. This means that the Na atoms have been _____________. (a) protonated. (b) oxidized. (c) hydrogenated. (d) reduced.

Which combination of answers best completes the following statement: When atoms are held together by ___________ __________, they are typically referred to as _________. (a) hydrogen bonds, molecules. (b) ionic interactions, salts. (c) ionic interactions, molecules. (d) double bonds, nonpolar.

Which of the following choices best describes the role of the lysosome? (a) transport of material to the Golgi (b) clean-up, recycling, and disposal of macromolecules (c) sorting of transport vesicles (d) the storage of excess macromolecules

Which of the following is nota feature commonly observed in βsheets? (a) antiparallel regions (b) coiled-coil patterns (c) extended polypeptide backbone (d) parallel regions

Which of the following is true for a reaction at equilibrium? (a) ΔG = ΔG° (b) ΔG° + RT ln [X]/[Y] = 0 (c) RT ln [X]/[Y] = 0 (d) ΔG + ΔG° = RT ln [X]/[Y]

Which of the following methods would be the most suitable to assess the relative purity of a protein in a sample you have prepared? (a) gel-ﬁltration chromatography (b) gel electrophoresis (c) western blot analysis (d) ion-exchange chromatography

Which of the following monomer building blocks is necessary to assemble selectively permeable boundaries around and inside cells? (a) sugars (b) fatty acids (c) amino acids (d) nucleotides

Which of the following organelles has both an outer and an inner membrane? (a) endoplasmic reticulum (b) mitochondrion (c) lysosome (d) peroxisome

Which of the following statements would not be true of a favorable binding equilibrium? (a) The free-energy change is negative for the system. (b) The concentration of the complex remains lower than the concentration of the unbound components. (c) The complex dissociation rate is slower than the rate for component association. (d) The binding energy for the association is large and negative.

Which statement is NOT true about the events/conclusions from studies during the mid-1800s surrounding the discovery of cells? (a) Cells came to be known as the smallest universal building block of living organisms. (b) Scientists came to the conclusion that new cells can form spontaneously from the remnants of ruptured cells. (c) Light microscopy was essential in demonstrating the commonalities between plant and animal tissues. (d) New cells arise from the growth and division of previously existing cells.

Which subatomic particles contribute to the atomic mass for any given element? (a) protons (b) protons and neutrons (c) neutrons (d) protons and electrons

You wish to explore how mutations in specific genes affecting sugar metabolism might alter tooth development. Which organism is likely to provide the best model system for your studies, and why? (a) horses (b) mice (c) E. coli (d) Arabidopsis

Your body extracts energy from the food you ingest by catalyzing reactions that essentially "burn" the food molecules in a stepwise fashion. What is another way to describe this process? (a) reduction (b) oxidation (c) dehydration (d) solvation

Which of the following is not true of molecular chaperones? (a) They assist polypeptide folding by helping the folding process follow the most energetically favorable pathway. (b) They can isolate proteins from other components of the cells until folding is complete. (c) They can interact with unfolded polypeptides in a way that changes the ﬁnal fold of the protein. (d) They help streamline the protein-folding process by making it a more efﬁcient and reliable process inside the cell.

Which of the following mechanisms best describes the manner in which lysozyme lowers the energy required for its substrate to reach its transition-state conformation? (a) by binding two molecules and orienting them in a way that favors a reaction between them (b) by altering the shape of the substrate to mimic the conformation of the transition state (c) by speeding up the rate at which water molecules collide with the substrate (d) by binding irreversibly to the substrate so that it cannot dissociate

Which of the following methods used to study proteins is limited to proteins with a molecular mass of 50 kD or less? (a) X-ray crystallography (b) ﬁngerprinting (c) nuclear magnetic resonance (d) mass spectroscopy

Which of the following methods would be the most suitable to assess levels of expression of your target protein in different cell types? (a) gel-ﬁltration chromatography (b) gel electrophoresis (c) western blot analysis (d) ion-exchange chromatography

Which of the following reagents are most likely to revitalize your reaction? (a) a vast excess of ATP (b) glucose 6-phosphate and enzyme D (c) creatine phosphate and enzyme A (d) pyrophosphate

Which of the following statements is true? (a) Disulﬁde bonds are formed by the cross-linking of methionine residues. (b) Disulﬁde bonds are formed mainly in proteins that are retained within the cytosol. (c) Disulﬁde bonds stabilize but do not change a protein's ﬁnal conformation. (d) Agents such as mercaptoethanol can break disulﬁde bonds through oxidation.

Which of the following statements is true? (a) Peptide bonds are the only covalent bonds that can link together two amino acids in proteins. (b) The polypeptide backbone is free to rotate about each peptide bond. (c) Nonpolar amino acids tend to be found in the interior of proteins. (d) The sequence of the atoms in the polypeptide backbone varies between different proteins.

Which statement is NOT true about mutations? (a) A mutation is a change in the DNA that can generate offspring less fit for survival than their parents. (b) A mutation can be a result of imperfect DNA duplication. (c) A mutation is a result of sexual reproduction. (d) A mutation is a change in the DNA that can generate offspring that are as fit for survival as their parents are.

Which subatomic particles can vary between isotopes of the same element, without changing the observed chemical properties? (a) electrons (b) protons and neutrons (c) neutrons (d) neutrons and electrons

Zebrafish (Danio rerio) are especially useful in the study of early development because their embryos ______________. (a) are exceptionally large. (b) develop slowly. (c) are transparent. (d) are pigmented.

__________ are fairly small organelles that provide a safe place within the cell to carry out certain biochemical reactions that generate harmful, highly reactive oxygen species. These chemicals are both generated and broken down in the same location. (a) Nucleosomes (b) Lysosomes (c) Peroxisomes (d) Endosomes

7-58 The concentration of a particular protein, X, in a normal human cell rises gradually from a low point, immediately after cell division, to a high point, just before cell division, and then drops sharply. The level of its mRNA in the cell remains fairly constant throughout this time. Protein X is required for cell growth and survival, but the drop in its level just before cell division is essential for division to proceed. You have isolated a line of human cells that grow in size in culture but cannot divide, and on analyzing these mutants, you find that levels of X mRNA in the mutant cells are normal. Which of the following mutations in the gene for X could explain these results? (a) the introduction of a stop codon that truncates protein X at the fourth amino acid (b) a change of the first ATG codon to CCA (c) the deletion of a sequence that encodes sites at which ubiquitin can be attached to the protein (d) a change at a splice site that prevents splicing of the RNA

c) the deletion of a sequence that encodes sites at which ubiquitin can be attached to the protein

A chemical reaction is deﬁned as spontaneous if there is a net loss of free energy during the reaction process. However, spontaneous reactions do not always occur rapidly. Favorable biological reactions require ______________ to selectively speed up reactions and meet the demands of the cell. (a) heat (b) ATP (c) ions (d) enzymes

Activated carriers are small molecules that can diffuse rapidly and be used to drive biosynthetic reactions in the cell. Their energy is stored in a readily transferable form such as high-energy electrons or chemical groups. Which of the molecules below is the most widely used activated carrier? (a) FADH2 (b) NADH (c) NADPH (d) ATP

Although all protein structures are unique, there are common structural building blocks that are referred to as regular secondary structures. Some proteins have α helices, some have β sheets, and still others have a combination of both. What makes it possible for proteins to have these common structural elements? (a) speciﬁc amino acid sequences (b) side-chain interactions (c) the hydrophobic-core interactions (d) hydrogen bonds along the protein backbone

An ionic bond between two atoms is formed as a result of the ______________. (a) sharing of electrons. (b) loss of electrons from both atoms. (c) loss of a proton from one atom. (d) transfer of electrons from one atom to the other.

Biologists cannot possibly study all living species. Instead, they try to understand cell behavior by studying a select subset of them. Which of the following characteristics are useful in an organism chosen for use as a model in laboratory studies? (a) amenability to genetic manipulation (b) ability to grow under controlled conditions (c) rapid rate of reproduction (d) all of the above

Cell biologists employ targeted fluorescent dyes or modified fluorescent proteins in both standard fluorescence microscopy and confocal microscopy to observe specific details in the cell. Even though fluorescence permits better visualization, the resolving power is essentially the same as that of a standard light microscope because the resolving power of a microscope is limited by the __________ of light. (a) absorption (b) intensity (c) filtering (d) wavelength

Cells require one particular monosaccharide as a starting material to synthesize nucleotide building blocks. Which of the monosaccharides below ﬁlls this important role? (a) glucose (b) fructose (c) ribulose (d) ribose

Chloroplasts are found only in eukaryotic cells that carry out photosynthesis: plants and algae. Plants and algae appear green as a result of the presence of chlorophyll. Where is chlorophyll located in the chloroplast? (a) in the first, outer membrane (b) in the space between the first and second membranes (c) in the second, inner membrane (d) in the third, innermost membrane

Choose the answer that best ﬁts the following statement: Cholesterol is an essential component of biological membranes. Although it is much smaller than the typical phospholipids and glycolipids in the membrane, it is a(n) _________________ molecule, having both hydrophilic and hydrophobic regions. (a) polar (b) oxygen-containing (c) hydrophobic (d) amphipathic

Despite the differences between eukaryotic and prokaryotic cells, prokaryotes have proteins that are distantly related to eukaryotic actin filaments and microtubules. What is likely to be the most ancient function of the cytoskeleton? (a) cell motility (b) vesicle transport (c) membrane support (d) cell division

If proteins to the dimeric A and B have complementary surfaces, they may interact form complex AB. Which of the following is the correct way to calculate the equilibrium constant for the association between A and B? (a) kon/koff = K (b) K = [A][B]/[AB] (c) K = [AB]/[A][B] (d) (a) and (c)

In the case of a simple conversion reaction such as X◊Y, which value of ΔG° is associated with a larger concentration of X than Y at equilibrium? (Hint: How is ΔG° related to K?) (a) ΔG° = -5 (b) ΔG° = -1 (c) ΔG° = 0 (d) ΔG° = 1

Lysozyme is an enzyme that speciﬁcally recognizes bacterial polysaccharides, which renders it an effective antibacterial agent. Into what classiﬁcation of enzymes does lysozyme fall? (a) isomerase (b) protease (c) nuclease (d) hydrolase

Macromolecules in the cell can often interact transiently as a result of noncovalent interactions. These weak interactions also produce stable, highly speciﬁc interactions between molecules. Which of the factors below is the most signiﬁcant in determining whether the interaction will be transient or stable? (a) the size of each molecule (b) the concentration of each molecule (c) the rate of synthesis (d) surface complementarity between molecules

Many types of cells have stores of lipids in their cytoplasm, usually seen as fat droplets. What is the lipid most commonly found in these droplets? (a) cholesterol (b) palmitic acid (c) isoprene (d) triacylglycerol

Molecular chaperones can work by creating an "isolation chamber." What is the purpose of this chamber? (a) The chamber acts as a garbage disposal, degrading improperly folded proteins so that they do not interact with properly folded proteins. (b) This chamber is used to increase the local protein concentration, which will help speed up the folding process. (c) This chamber serves to transport unfolded proteins out of the cell. (d) This chamber serves to protect unfolded proteins from interacting with other proteins in the cytosol, until protein folding is completed.

Motor proteins use the energy in ATP to transport organelles, rearrange elements of the cytoskeleton during cell migration, and move chromosomes during cell division. Which of the following mechanisms is sufﬁcient to ensure the unidirectional movement of a motor protein along its substrate? (a) A conformational change is coupled to the release of a phosphate (Pi). (b) The substrate on which the motor moves has a conformational polarity. (c) A conformational change is coupled to the binding of ADP. (d) A conformational change is linked to ATP hydrolysis.

NADH and NADPH are activated carrier molecules that function in completely different metabolic reactions. Both carry two additional ________ and one additional _____________. This combination can also be referred to as a hydride ion. (a) protons, electron. (b) electrons, phosphate. (c) hydrogens, electron. (d) electrons, proton.

Polar covalent bonds are formed when the electrons in the bond are not shared equally between the two nuclei. Which one of these molecules contains polar bonds? (a) molecular oxygen (b) methane (c) propane (d) water

Prokaryotic cells are able to evolve very fast, which helps them to rapidly adapt to new food sources and develop resistance to antibiotics. Which of the options below lists the three main characteristics that support the rapid evolution of prokaryotic populations? (a) microscopic, motile, anaerobic (b) aerobic, motile, rapid growth (c) no organelles, cell wall, can exchange DNA (d) large population, rapid growth, can exchange DNA

Protein structures have several different levels of organization. The primary structure of a protein is its amino acid sequence. The secondary and tertiary structures are more complicated. Consider the deﬁnitions below and select the one that best ﬁts the term "protein domain." (a) a small cluster of α helices and β sheets (b) the tertiary structure of a substrate-binding pocket (c) a complex of more than one polypeptide chain (d) a protein segment that folds independently

Select the answer that best completes the following statement: Chemical reactions in living systems occur in an ____________ environment, within a narrow range of temperatures. (a) optimal (b) organic (c) extracellular (d) aqueous

The Ras protein is a GTPase that functions in many growth-factor signaling pathways. In its active form, with GTP bound, it transmits a downstream signal that leads to cell proliferation; in its inactive form, with GDP bound, the signal is not transmitted. Mutations in the gene for Ras are found in many cancers. Of the choices below, which alteration of Ras activity is most likely to contribute to the uncontrolled growth of cancer cells? (a) a change that prevents Ras from being made (b) a change that increases the afﬁnity of Ras for GDP (c) a change that decreases the afﬁnity of Ras for GTP (d) a change that decreases the rate of hydrolysis of GTP by Ras

The __________ __________ is made up of two concentric membranes and is continuous with the membrane of the endoplasmic reticulum. (a) plasma membrane (b) Golgi network (c) mitochondrial membrane (d) nuclear envelope

The cell constantly exchanges materials by bringing nutrients in from the external environment and shuttling unwanted by-products back out. Which term describes the process by which external materials are captured inside vesicles and brought into the cell? (a) degradation (b) exocytosis (c) phagocytosis (d) endocytosis

The correct folding of proteins is necessary to maintain healthy cells and tissues. Unfolded proteins are responsible for such neurodegenerative disorders as Alzheimer's disease, Huntington's disease, and Creutzfeldt-Jakob disease (the speciﬁc faulty protein is different for each disease). What is the ultimate fate of these disease-causing, unfolded proteins? (a) They are degraded. (b) They bind a different target protein. (c) They form structured ﬁlaments. (d) They form protein aggregates.

The energy used by the cell to generate speciﬁc biological molecules and highly ordered structures is stored in the form of _____________. (a) Brownian motion. (b) heat. (c) light waves. (d) chemical bonds.

The maximum velocity (Vmax) of an enzymatic reaction is an important piece of information regarding how the enzyme works. What series of measurements can be taken in order to infer the maximum velocity of an enzyme-catalyzed reaction? (a) the rate of substrate consumption after the system reaches equilibrium, for several reactant concentrations (b) the rate of product consumption shortly after mixing the enzyme and substrate (c) the rate of substrate consumption at high levels of enzyme concentration (d) the rate of substrate consumption shortly after mixing the enzyme and substrate, for several substrate concentrations

The pH of an aqueous solution is an indication of the concentration of available protons. However, you should not expect to ﬁnd lone protons in solution; rather, the proton is added to a water molecule to form a(n) ______________ ion. (a) hydroxide (b) ammonium (c) chloride (d) hydronium

The study of enzyme kinetics is usually performed with puriﬁed components and requires the characterization of several aspects of the reaction, including the rate of association with the substrate, the rate of catalysis, and _____________. (a) the enzyme's structure. (b) the optimal pH of the reaction. (c) the subcellular localization of the enzyme. (d) the regulation of the enzyme activity

What unit of length would you generally use to measure a typical plant or animal cell? (a) centimeters (b) nanometers (c) millimeters (d) micrometers

Which of the following characteristics would not support the idea that the ancestral eukaryote was a predator cell that captured and consumed other cells? (a) dynamic cytoskeleton (b) large cell size (c) ability to move (d) rigid membrane

Which of the following is not thought to contribute to diversity in the genome of human individuals?

exon shuffling

Indicate whether the following statements are true or false. Lysosomes are small organelles where fatty acid synthesis occurs.

false

Indicate whether the following statements are true or false. Plants do not require a cytoskeleton because they have a cell wall that lends structure and support to the cell.

false

Indicate whether the following statements are true or false. The Paramecium is a multicellular microorganism covered with hair-like cilia.

false

Indicate whether the following statements are true or false. The cytosol is fairly empty, containing a limited number of organelles, which allows room for rapid movement via diffusion.

false

Indicate whether the following statements are true or false. The nucleus of an animal cell is round, small, and difficult to distinguish using light microscopy.

false

Indicate whether the following statements are true or false. The number of mitochondria inside a cell remains constant over the life of the cell.

false

Indicate whether the following statements are true or false. The terms "prokaryote" and "bacterium" are synonyms.

false

Indicate whether the following statements are true or false. Photosynthetic bacteria contain chloroplasts.

false

Indicate whether the following statements are true or false. With respect to cellular respiration, the only organelles used by animal cells are mitochondria, while plant cells use both mitochondria and chloroplasts.

false

Indicate whether the following statements are true or false. Mitochondria are thought to have evolved from anaerobic bacteria.

false

True or false Horizontal gene transfer is very rare and this has had little influence on the genomes of bacteria

false

True or false Most genes in veterbrates are unique and only a few genes are members of multigene families

false

Indicate whether the following statements about enzymes are true or false. If a statement is false, explain why it is false. A. Enzymes alter the equilibrium point of a reaction. B. Vmax can be determined by measuring the amount of product accumulated late in the reaction. C. Competitive inhibitors bind irreversibly to the enzyme active site, lowering Vmax

false false false

Indicate whether a is false, explain the following statements are true or false A. The second law of thermodynamics states that the total amount of energy in the Universe does not change. B. The ultimate source of energy for living systems is chlorophyll. C. CO2 gas is ﬁxed in a series of reactions that are light-dependent. D. H2 is the most stable and abundant form of hydrogen in the environment.

false false false false

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. The amino acids in the interior of a protein do not interact with the ligand and do not play a role in selective binding. B. Antibodies are Y-shaped and are composed of six different polypeptide chains. C. ATPases generate ATP for the cell. D. Hexokinase recognizes and phosphorylates only one of the glucose stereoisomers.

false false false true

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Generally, the total number of nonpolar amino acids has a greater effect on protein structure than the exact order of amino acids in a polypeptide chain. B. The "polypeptide backbone" refers to all atoms in a polypeptide chain, except for those that form the peptide bonds. C. The chemical properties of amino acid side chains include charged, uncharged polar, and nonpolar. D. The relative distribution of polar and nonpolar amino acids in a folded protein is determined largely by hydrophobic interactions, which favor the clustering of nonpolar side chains in the interior.

false false true true

Indicate whether the following statements are true or false. A. Primitive plant, animal, and fungal cells probably acquired mitochondria after they diverged from a common ancestor. B. Protozoans are single-celled eukaryotes with cell morphologies and behaviors that can be as complex as those of some multicellular organisms. C. The first eukaryotic cells on Earth must have been aerobic; otherwise, they would not have been able to survive when the planet's atmosphere became oxygen-rich.

false true false

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Van der Waals interactions and hydrophobic interactions are two ways to describe the same type of weak forces that help proteins fold. B. A large number of noncovalent interactions is required to hold two regions of a polypeptide chain together in a stable conformation. C. A single polypeptide tends to adopt 3-4 different conformations, which all have equivalent free-energy values (G).

false true false

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. A disaccharide consists of a sugar covalently linked to another molecule such as an amino acid or a nucleotide. B. The hydroxyl groups on monosaccharides are reaction hot spots and can be replaced by other functional groups to produce derivatives of the original sugar. C. The presence of double bonds in the hydrocarbon tail of fatty acid does not greatly inﬂuence its structure.

false true false

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. The chemistry of life is carried out and coordinated primarily by the action of small molecules. B. Carbon-based compounds make up the vast majority of molecules found in cells. C. The chemical reactions in living systems are loosely regulated, allowing for a wide range of products and more rapid evolution.

false true false

5-58 Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. The histone proteins that constitute the core nucleosome include tetramers of histones H2A, H2B, H3, and H4. B. Linker histones help compact genomic DNA by influencing the path of the DNA after it has wrapped about the nucleosome core. C. Histone proteins have a lower-than-average number of lysines and arginines in their polypeptide chains. D. Interphase chromosomes represent a physical state of the chromatin with the highest order of packaging.

false true false false

5-7 Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. DNA molecules, like proteins, consist of a single, long polymeric chain that is assembled from small monomeric subunits. B. The polarity of a DNA strand results from the polarity of the nucleotide subunits. C. There are five different nucleotides that become incorporated into a DNA strand. D. Hydrogen bonds between each nucleotide hold individual DNA strands together.

false true false false

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Feedback inhibition is deﬁned as a mechanism of down-regulating enzyme activity by the accumulation of a product earlier in the pathway. B. If an enzyme's allosteric binding site is occupied, the enzyme may adopt an alternative conformation that is not optimal for catalysis. C. Protein phosphorylation is another way to alter the conformation of an enzyme and serves exclusively as a mechanism to increase enzyme activity. D. GTP-binding proteins typically have GTPase activity, and the hydrolysis of GTP transforms them to the "off" conformation.

false true false true

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. "Nonpolar interactions" is simply another way of saying "van der Waals attractions." B. Condensation reactions occur in the synthesis of all the macromolecules found in cells. C. All proteins and RNAs pass through many unstable conformations as they are folded, ﬁnally settling on one single, preferred conformation.

false true true

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. Any covalently bonded H atom can participate in a hydrogen bond if it comes in close proximity with an oxygen atom that forms part of a water molecule. B. Protons are constantly moving between water molecules, which means there is an overall equilibrium between hydroxyl ions and hydronium ions in aqueous solutions. C. A can from strong base is deﬁned as a molecule that readily remove protons water.

false true true

5-42 Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Comparing the relative number of chromosome pairs is a good way to determine whether two species are closely related. B. Chromosomes exist at different levels of condensation, depending on the stage of the cell cycle. C. Eukaryotic chromosomes contain many different sites where DNA replication can be initiated. D. The telomere is a specialized DNA sequence where microtubules from the mitotic spindle attach to the chromosome so that duplicate copies move to opposite ends of the dividing cell.

false true true false

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. When two macromolecules form a complex, the free energy of the system increases because there is a net increase in the amount of order in the cell. B. Sequential pathways can help drive unfavorable reactions by siphoning off the products into the next energetically favorable reaction in the series. C. The cytosol is densely packed with molecules, creating what is more an aqueous gel than a solution. D. The diffusion rates for smaller molecules in the cytosol are much lower than what is observed for the same molecules in water.

false true true false

Which of the following statements are true or false? If a statement is false, explain why it is false. A. Enzymes lower the free energy released by the reaction that they facilitate. B. Enzymes lower the activation energy for a speciﬁc reaction. C. Enzymes increase the probability that any given reactant molecule will be converted to product. D. Enzymes increase the average energy of reactant molecules

false true true false

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Photosynthetic organisms release only O2 into the atmosphere, while nonphotosynthetic organisms release only CO2. B. The cycling of carbon through the biosphere ﬁrst requires the incorporation of inorganic CO2 into organic molecules. C. The oxidation of one molecule is always coupled to the reduction of a second molecule. D. During cellular respiration, carbon-containing molecules become successively more oxidized until they reach their most oxidized form, as CO2.

false true true true

For each of the following pairs of gene functions, choose the one that is more likely to be highly reserved. A. genes involved in sexual reproduction/genes involved in sugar metabolism B. DNA replication/ developmental pathways C. hormone production/ lipid synthesis

genes involved in sugar metabolism, DNA replication, lipid synthesis

Indicate whether the following statements are true or false. If the statement is false, explain why it is false. A. The human genome is roughly 30 times larger than the Arabidopsis genome, but contains approximately the same number of protein-coding genes. B. The variation in genome size among protozoans is larger than that observed across all species of mammals, birds, and reptiles. C. The vast majority of our genome encodes functional RNA molecules or proteins and most of the intervening DNA is nonfunctional.

true true false

On the basis of the two reactions below, decide which of the following statements are true and which are false. If a statement is false, explain why it is false. 1: ATP + Y ◊ Y-P + ADP ΔG = -100 kcal/mole 2: Y-P + A ◊ B ΔG = 50 kcal/mole A. Reaction 1 is favorable because of the large negative ΔG associated with the hydrolysis of ATP. B. Reaction 2 is an example of an unfavorable reaction. C. Reactions 1 and 2 are coupled reactions, and when they take place together, reaction 2 will proceed in the forward direction. D. Reaction 2 can be used to drive reaction 1 in the reverse direction.

true true true false

5-34 The human genome is divided into linear segments and packaged into structures called chromosomes. What is the total number of chromosomes found in each of the somatic cells in your body? (a) 22 (b) 23 (c) 44 (d) 46

Which of the following statements is false? (a) A mutation that arises in a mother's somatic cell often causes a disease in her daughter. (b) All mutations in an asexually reproducing single-celled organism are passed on to progeny (c) In an evolutionary sense, somatic cells exist only to help propagate germ line cells (d) A mutation is passed on only if it is present in the germ line

(a) A mutation that arises in a mother's somatic cell often causes a disease in her daughter

Which of the following statements about gene families is false? (a) Because gene duplication can occur when crossover events occur, genes are always duplicated onto homologous chromosomes (b) Not all duplicated genes will become functional members of gene families (c) Whole genome duplication can contribute to the formation of gene families (d) Duplicated genes can diverge in both their regulatory and coding regions

(a) Because gene duplication can occur when crossover events occur, genes are always duplicated onto homologous chromosomes

which of the following statements about homologous genes is true? (a) For protein coding genes, homologous genes will show more similarity in their amino acid sequences than in their nucleotide sequences (b) Fewer than 1% of human genes have homologs in the nematode and the fruit fly (c) Most homologous genes arose by gene duplication

(a) For protein coding genes, homologous genes will show more similarity in their amino acid sequences than in their nucleotides sequences

The pufferfish, fugu rubripes, has a genome that is one-tenth the size of mammalian genomes. Which of the following is not a possible reason for this size difference? (a) Fugu has lost many genes that are part of gene families (b) intron sequences in Fugu are shorter than those in mammals (c) Fugu lacks the repetitive DNA found in mammals (d) The fugu genome seems to have lost sequences faster than it has gained them over evolutionary times

(a) Fugu has lost many genes that are part if gene families

7-33 Genes in eukaryotic cells often have intronic sequences coded for within the DNA. These sequences are ultimately not translated into proteins. Why? (a) Intronic sequences are removed from RNA molecules by the spliceosome, which works in the nucleus. (b) Introns are not transcribed by RNA polymerase. (c) Introns are removed by catalytic RNAs in the cytoplasm. (d) The ribosome will skip over intron sequences when translating RNA into protein.

(a) Intronic sequences are removed from RNA molecules by the spliceosome, which works in the nucleus.

Which of the following is true of a retrovirus but not the Alu retrotransoposion? (a) It encodes its own reverse transcriptase (b) it requires cellular enzymes to make copies (c) it can be excised and moved to a new location in the genome

(a) It encodes its own reverse transcriptase

Which of the statements about what we have learned by comparing modern-day human genome to other genomes is true? (a) Modern humans whose ancestors are from Europe or Asia share up to 4% of their genome with Neanderthals (b) The human genome is far more gene-dense than the yeast genome

(a) Modern humans whose ancestors are from Europe or Asia share up to 4% of their genome with Neanderthals

8-50 In mammals, individuals with two X chromosomes are female, and individuals with an X and a Y chromosome are male. It had long been known that a gene located on the Y chromosome was sufficient to induce the gonads to form testes, which is the main male-determining factor in development, and researchers sought the product of this gene, the so-called testes- determining factor (TDF). For several years, the TDF was incorrectly thought to be a zinc finger protein encoded by a gene called BoY. Which of the following observations would most strongly suggest that BoY might not be the TDF? Explain your answer. (a) Some XY individuals that develop into females have mutations in a different gene, SRY, but are normal at BoY. (b) BoY is not expressed in the adult male testes. (c) Expression of BoY in adult females does not masculinize them. (d) A few of the genes that are known to be expressed only in the testes have binding sites for the BoY protein in their upstream regulatory sequences, but most do not.

(a) Some XY individuals that develop into females have mutations in a different gene, SRY, but are normal at BoY.

8-13 Which of the following statements about the Lac operon is false? (a) The Lac repressor binds when lactose is present in the cell. (b) Even when the CAP activator is bound to DNA, if lactose is not present, the Lac operon will not be transcribed. (c) The CAP activator can only bind DNA when it is bound to cAMP. (d) The Lac operon only produces RNA when lactose is present and glucose is absent.

(a) The Lac repressor binds when lactose is present in the cell.

8-44 You are studying a set of mouse genes whose expression increases when cells are exposed to the hormone cortisol, and you believe that the same cortisol- responsive transcriptional activator regulates all of these genes. Which of the following statements below should be true if your hypothesis is correct? (a) The cortisol-responsive genes share a DNA sequence in their regulatory regions that binds the cortisol-responsive transcriptional activator. (b) The cortisol-responsive genes must all be in an operon. (c) The transcriptional regulators that bind to the regulatory regions of the cortisol-responsive genes must all be the same. (d) The cortisol-responsive genes must not be transcribed in response to other hormones.

(a) The cortisol-responsive genes share a DNA sequence in their regulatory regions that binds the cortisol-responsive transcriptional activator.

Which of the following statements is true? (a) The intron structure of most genes is conserved among vertebrates (b) the more nucleotides there are in a genome, the more genes there will be in its genome

(a) The intron structure of most genes is conserved among vertebrates

7-27 Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus? (a) The ribosome binds to the mRNA. (b) The mRNA is polyadenylated at its 3′ end. (c) 7-methylguanosine is added in a 5′-to-5′ linkage to the mRNA. (d) RNA polymerase dissociates.

(a) The ribosome binds to the mRNA.

8-10 Which of the following statements about transcriptional regulators is false? (a) Transcriptional regulators usually interact with the sugar-phosphate backbone on the outside of the double helix to determine where to bind on the DNA helix. (b) Transcriptional regulators will form hydrogen bonds, ionic bonds, and hydrophobic interactions with DNA. (c) The DNA-binding motifs of transcriptional regulators usually bind in the major groove of the DNA helix. (d) The binding of transcriptional regulators generally does not disrupt the hydrogen bonds that hold the double helix together.

(a) Transcriptional regulators usually interact with the sugar-phosphate backbone on the outside of the double helix to determine where to bind on the DNA helix.

Which of the following changes is least likely to arise from a point mutation in a regulatory region of a gene? (a) a mutation that changes the subcellular localization of a protein (b) a mutation that changes the time in an organisms life during which a protein is expressed (c) a mutation that eliminates the production of a protein in a specific cell type (d) a mutation that increases the level of protein production in a cell

(a) a mutation that changes the subcellular localization of a protein

You discover that the underlying cause of a disease is a protein that is now less stable than the non-disease-causing version of the protein. This change is most likely due to ______________. (a) a mutation within a gene (b) a mutation within a regulatory DNA of a gene (c) gene duplication (d) horizontal gene transfer

(a) a mutation within a gene

If this hypothesis is true, which of the following types of genetic change would most likely lead to this situation? (a) a mutation within an upstream enhancer of the gene (b) a mutation within the transcription factor gene that leads to a premature stop codon after the third amino acid (c) a mutation within the transcription factor gene that leads to a substitution of a positively charged amino acid for a negatively charged amino acid\ (d) a mutation in the TATA box of the gene

(a) a mutation within an upstream enhancer of the gene

Which of the following generalities about genomes is true? (a) All vertebrate genomes contain roughly the same number of genes (b) all unicellular organisms contain the same number of genes (c) the larger the organism, the more genes it has (d) the more types of cell an organsim has the more genes it hs

(a) all verterbrate genomes contain roughly the same number of genes

8-58 MicroRNAs ____________________. (a) are produced from a precursor miRNA transcript. (b) are found only in humans. (c) control gene expression by base-pairing with DNA sequences. (d) can degrade RNAs by using their intrinsic catalytic activity

(a) are produced from a precursor miRNA transcript.

8-56 miRNAs, tRNAs, and rRNAs all _____________. (a) do not code for proteins. (b) act in the nucleus. (c) are packaged with other proteins to form RISC. (d) form base pairs with mRNA molecules.

(a) do not code for proteins.

Nonhomologous end joining can result in all but which of the following? (a) the recovery of lost nucleotides on a damaged DNA strand (b) the interruption of gene expression (c) loss of nucleotides at the site of repair (d) translocations of DNA fragments to an entirely different chromosome

8-6 Investigators performed nuclear transplant experiments to determine whether DNA is altered irreversibly during development. Which of the following statements about these experiments is true? (a) Because the donor nucleus is taken from an adult animal, the chromosomes from the nucleus must undergo recombination with the DNA in the egg for successful development to occur. (b) The embryo that develops from the nuclear transplant experiment is genetically identical to the donor of the nucleus. (c) The meiotic spindle of the egg must interact with the chromosomes of the injected nuclei for successful nuclear transplantation to occur. (d) Although nuclear transplantation has been successful in producing embryos in some mammals with the use of foster mothers, evidence of DNA alterations during differentiation has not been obtained for plants.

(b) The embryo that develops from the nuclear transplant experiment is genetically identical to the donor of the nucleus.

8-54 Which of the following statements about mRNA half-life is false? (a) The half-life of mRNAs produced from different genes will vary more than the half-life of mRNAs produced from the same gene. (b) The half-life of most eukaryotic-cell mRNAs is >24 hours. (c) The half-life of most bacterial mRNAs is shorter than the half-life of a typical eukaryotic mRNA. (d) The 5′ and 3′ untranslated regions of an mRNA often contain specific sequences that determine the lifetime of the mRNA molecule

(b) The half-life of most eukaryotic-cell mRNAs is >24 hours.

Which of the following about retroviruses is false? (a) They are packed with a few molecules of reverse t. in each virus particle (b) They use the host-genome integrase enzyme to create provirus (c) The production of viral RNAs can occur long after the initial infection of the host cell by the retrovirus (d) viral RNAs are translated by host cell ribosomes to produce the proteins required for the production of viral particles

(b) They use the host-genome integrase enzyme to create provirus

8-12 The tryptophan operator ___________________________. (a) is an allosteric protein. (b) binds to the tryptophan repressor when the repressor is bound to tryptophan. (c) is required for production of the mRNA encoded by the tryptophan operon. (d) is important for the production of the tryptophan repressor.

(b) binds to the tryptophan repressor when the repressor is bound to tryptophan.

8-36 How are most eukaryotic transcription regulators able to affect transcription when their binding sites are far from the promoter? (a) by binding to their binding site and sliding to the site of RNA polymerase assembly (b) by looping out the intervening DNA between their binding site and the promoter (c) by unwinding the DNA between their binding site and the promoter (d) by attracting RNA polymerase and modifying it before it can bind to the promoter

(b) by looping out the intervening DNA between their binding site and the promoter

8-45 Which of the following statements about iPS cells is false? (a) iPS cells are created by adding a combination of transcription regulators to a fibroblast. (b) iPS cells created from mouse cells can differentiate into almost any human cell type. (c) Stimulation by extracellular signal molecules causes iPS cells to differentiate. (d) During the de-differentiation process to become an iPS, the fibroblast will undergo changes to its gene expression profile.

(b) iPS cells created from mouse cells can differentiate into almost any human cell type.

8-43 Combinatorial control of gene expression __________________________. (a) involves every gene using a different combination of transcriptional regulators for its proper expression. (b) involves groups of transcriptional regulators working together to determine the expression of a gene. (c) involves only the use of gene activators used together to regulate genes appropriately. (d) is seen only when genes are arranged in operons.

(b) involves groups of transcriptional regulators working together to

7-54 In eukaryotes, but not in prokaryotes, ribosomes find the start site of translation by ____________________________. (a) binding directly to a ribosome-binding site preceding the initiation codon. (b) scanning along the mRNA from the 5′ end. (c) recognizing an AUG codon as the start of translation. (d) binding an initiator tRNA.

(b) scanning along the mRNA from the 5′ end.

8-63 The owners of a local bakery ask for your help in improving a special yeast strain they use to make bread. They would like you to help them design experiments using RNA interference to turn off genes, to allow them to test of the following statements about RNAi is true? their hypothesis that certain genes are important for the good flavors found in their bread. Of the components in the following list, which is the most important to check for in this yeast strain if you'd like this project to succeed? (a) the presence of foreign double-stranded RNA (b) the presence of genes in the genome that code for RISC proteins (c) the presence of miRNA genes in the genome (d) the presence of single-stranded siRNAs within the cell

(b) the presence of genes in the genome that code for RISC proteins

8-2 The distinct characteristics of different cell types in a multicellular organism result mainly from the differential regulation of the _________________. (a) replication of specific genes. (b) transcription of genes transcribed by RNA polymerase II. (c) transcription of housekeeping genes. (d) proteins that directly bind the TATA box of eukaryotic genes.

(b) transcription of genes transcribed by RNA polymerase II.

Given this information which of the following statements is true? (a) The ancestral globin gene arose 500 million years ago (b) the a-globin gene is more closely related to the e-globin gene than to the s-globin gene (c) The nucleotide sequences of the two y-globins will be most similar because they are closest together on the chromosome (d) The fetal B-globins arose from a gene duplication that occured 200 million years ago which gave rise to a B globin expressed in the fetus and a B globin expressed in the adult

(d)

Viral genomes _________________. (a) can be made of DNA (b) can be made of RNA (c) can be either double stranded or single (d) all of the above

(d)

There is an experiment used to determine the spontaneous mutation rate in E. coli. If the spontaneous mutation rate in E. coli is 1 mistake in every 10^9nucleotides copied, about how many colonies would you expect to see on the plates lacking histidine if you were to assay 10^11 cells from the culture for their ability to form colonies? (a) 1 (b) 2 (c) 10 (d) 100

(d) 100

How much nucleotide divergence is there on average between species M and N?

2.0%

A finished draft of the human genome was published in ___________.

2004

5-16 The DNA from two different species can often be distinguished by a difference in the ______________________. (a) ratio of A + T to G + C (b) ratio of A + G to C + T (c) ratio of sugar to phosphate (d) presence of bases other than A, G, C, and T

5-2 Many of the breakthroughs in modern biology came after Watson and Crick published their model of DNA in 1953. However, chromosomes were identified earlier. In what decade did scientists first identify chromosomes? (a) 1880s (b) 1920s (c) 1940s (d) 1780s

5-44 The chromosomes we typically see in images are isolated from mitotic cells. These mitotic chromosomes are in the most highly condensed form. Interphase cells contain chromosomes that are less densely packed and __________________________. (a) occupy discrete territories in the nucleus (b) share the same nuclear territory as their homolog (c) are restricted to the nucleolus (d) are completely tangled with other chromosomes

5-46 Specific regions of eukaryotic chromosomes contain sequence elements that are absolutely required for the proper transmission of genetic information from a mother cell to each daughter cell. Which of the following is not known to be one of these required elements in eukaryotes? (a) terminators of replication (b) origins of replication (c) telomeres (d) centromeres

5-47 Mitotic chromosomes are _____ times more compact than a DNA molecule in its extended form. (a) 10,000 (b) 100,000 (c) 1000 (d) 100

5-50 The classic "beads-on-a-string" structure is the most decondensed chromatin structure possible and is produced experimentally. Which chromatin components are not retained when this structure is generated? (a) linker histones (b) linker DNA (c) nucleosome core particles (d) core histones

5-62 Methylation and acetylation are common changes made to histone H3, and the specific combination of these changes is sometimes referred to as the "histone code." Which of the following patterns will probably lead to gene silencing? (a) lysine 9 methylation (b) lysine 4 methylation and lysine 9 acetylation (c) lysine 14 acetylation (d) lysine 9 acetylation and lysine 14 acetylation

5-64 Which of the following best describes the mechanism by which chromatin-remodeling complexes "loosen" the DNA wrapped around the core histones? (a) They use energy derived from ATP hydrolysis to change the relative position of the DNA and the core histone octamer (b) They chemically modify the DNA, changing the affinity between the histone octamer and the DNA (c) They remove histone H1 from the linker DNA adjacent to the core histone octamer (d) They chemically modify core histones to alter the affinity between the histone octamer and the DNA

5-8 Several experiments were required to demonstrate how traits are inherited. Which scientist or team of scientists first demonstrated that cells contain some component that can be transferred to a new population of cells and permanently cause changes in the new cells? (a) Griffith (b) Watson and Crick (c) Avery, MacLeod, and McCarty (d) Hershey and Chase

DNA polymerase catalyzes the joining of a nucleotide to a growing DNA strand. What prevents this enzyme from catalyzing the reverse reaction? (a) hydrolysis of pyrophosphate (PPi) to inorganic phosphate (Pi) + Pi (b) release of PPi from the nucleotide (c) hybridization of the new strand to the template (d) loss of ATP as an energy source

The repair of mismatched base pairs or damaged nucleotides in a DNA strand requires a multistep process. Which choice below describes the known sequence of events in this process? (a) DNA damage is recognized, the newly synthesized strand is identified by an existing nick in the backbone, a segment of the new strand is removed by repair proteins, the gap is filled by DNA polymerase, and the strand is sealed by DNA ligase. (b) DNA repair polymerase simultaneously removes bases ahead of it and polymerizes the correct sequence behind it as it moves along the template. DNA ligase seals the nicks in the repaired strand. (c) DNA damage is recognized, the newly synthesized strand is identified by an existing nick in the backbone, a segment of the new strand is removed by an exonuclease, and the gap is repaired by DNA ligase. (d) A nick in the DNA is recognized, DNA repair proteins switch out the wrong base and insert the correct base, and DNA ligase seals the nick.

What part of the DNA replication process would be most directly affected if a strain of bacteria lacking helicase were used to make the cell extracts? (a) initiation of DNA synthesis (b) Okazaki fragment synthesis (c) leading-strand elongation (d) lagging-strand completion

What part of the DNA replication process would be most directly affected if a strain of bacteria lacking primase were used to make the cell extracts? (a) initiation of DNA synthesis (b) Okazaki fragment synthesis (c) leading-strand elongation (d) lagging-strand completion

A pregnant mouse is exposed to high levels of a chemical. Many of the mice in her litter are deformed, but when they are interbred with each other, all their offspring are normal. Which two of the following statements could explain these results? (a) In the deformed mice, somatic cells but not germ cells were mutated. (b) The original mouse's germ cells were mutated. (c) In the deformed mice, germ cells but not somatic cells were mutated. (d) The toxic chemical affects development but is not mutagenic.

A and D

5-4 In the 1940s, proteins were thought to be the more likely molecules to house genetic information. What was the primary reason that DNA was not originally believed to be the genetic material? (a) DNA has a high density of negative charges (b) Nucleotides were known to be a source of chemical energy for the cell (c) Both protein and nucleic acids were found to be components of chromosomes (d) DNA was found to contain only four different chemical building blocks

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. When DNA is being replicated inside a cell, local heating occurs, allowing the two strands to separate. B. DNA replication origins are typically rich in G-C base pairs. C. Meselson and Stahl ruled out the dispersive model for DNA replication. D. DNA replication is a bidirectional process that is initiated at multiple locations along chromosomes in eukaryotic cells.

A. False B. False C. True. D. True.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. The repair polymerase is the enzyme that proofreads the newly synthesized strands to ensure the accuracy of DNA replication. B. There is a single enzyme that degrades the RNA primers and lays down the corresponding DNA sequence behind it. C. DNA ligase is required to seal the sugar-phosphate backbone between all the DNA fragments on the lagging strand. D. The repair polymerase does not require the aid of the sliding clamp, because it is only synthesizing DNA over very short stretches.

A. False. B. False. C. True. D. True.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Homologous recombination cannot occur in prokaryotic cells, because they are haploid, and therefore have no extra copy of the chromosome to use as a template for repair. B. The first step in repair requires a nuclease to remove a stretch of base pairs from the 5′ end of each strand at the site of the break. C. The 3′ overhang "invades" the homologous DNA duplex, which can be used as a primer for the repair DNA polymerase. D. The DNA template used to repair the broken strand is the homologous chromosome inherited from the other parent.

A. False. B. True. C. True. D. False.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Ionizing radiation and oxidative damage can cause DNA double-strand breaks. B. After damaged DNA has been repaired, nicks in the phosphate backbone are maintained as a way to identify the strand that was repaired. C. Depurination of DNA is a rare event that is caused by ultraviolet irradiation. D. Nonhomologous end joining is a mechanism that ensures that DNA double-strand breaks are repaired with a high degree of fidelity to the original DNA sequence.

A. True B. False. C. False. D. False.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Primase is needed to initiate DNA replication on both the leading strand and the lagging strand. B. The sliding clamp is loaded once on each DNA strand, where it remains associated until replication is complete. C. Telomerase is a DNA polymerase that carries its own RNA molecule to use as a primer at the end of the lagging strand. D. Primase requires a proofreading function that ensures there are no errors in the RNA primers used for DNA replication.

A. True. B. False. C. True. D. False.

5-12 Hershey and Chase used radiolabeled macromolecules to identify the material that contains heritable information. What radioactive material was used to track DNA during this experiment? (a) 3H (b) 14C (c) 35S (d) 32P

5-13 Which of the following chemical groups is not used to construct a DNA molecule? (a) five-carbon sugar (b) phosphate (c) nitrogen-containing base (d) six-carbon sugar

5-15 Which of the following DNA strands can form a DNA duplex by pairing with itself at each position? (a) 5′-AAGCCGAA-3′ (b) 5′-AAGCCGTT-3′ (c) 5′-AAGCGCAA-3′ (d) 5′-AAGCGCTT-3′

5-24 The complete set of information found in a given organism's DNA is called its ____________. (a) genetic code (b) coding sequence (c) gene (d) genome

When the polymer X-X-X... is broken down into monomers, it is "phosphorylyzed" rather than hydrolyzed, in the following repeated reaction: X-X-X... + P ◊ X-P + X-X... (reaction 1) Given the ΔG° values of the reactions listed in the following table, what is the expected ratio of X-phosphate (X-P) to free phosphate (P) at equilibrium for reaction 1? (a) 1:10 (b) 1:10 (c) 1:1 (d) 10:1

When there is an excess of nutrients available in the human body, insulin is released to stimulate the synthesis of glycogen from glucose. This is a speciﬁc example of a(n) __________ process, a general process in which larger molecules are made from smaller molecules. (a) metabolic (b) catabolic (c) anabolic (d) biosynthetic

Antibody production is an indispensible part of our immune response, but it is not the only defense our bodies have. Which of the following is observed during an infection that is not a result of antibody-antigen interactions? (a) B cell proliferation (b) aggregation of viral particles (c) systemic temperature increase (d) antibody secretion

At ﬁrst glance, it may seem that living systems are able to defy the second law of thermodynamics. However, on closer examination, it becomes clear that although cells create organization from raw materials in the environment, they also contribute to disorder in the environment by releasing _____________. (a) water. (b) radiation. (c) heat. (d) proteins.

Chemical reactions that lead to a release of free energy are referred to as "energetically favorable." Another way to describe these reactions is: _____________. (a) uphill. (b) uncatalyzed. (c) spontaneous. (d) activated.

Choose the phrase that best completes this sentence: Microtubules ____________ and are required to pull duplicated chromosomes to opposite poles of dividing cells. (a) generate contractile forces (b) are intermediate in thickness (c) can rapidly reorganize (d) are found in especially large numbers in muscle cells

Double covalent bonds are both shorter and stronger than single covalent bonds, but they also limit the geometry of the molecule because they ____________________. (a) create a new arrangement of electron shells. (b) change the reactivity of the bonded atoms. (c) limit the rotation of the bonded atoms. (d) prevent additional bonds from being formed with the bonded atoms.

Energy cannot be created or destroyed, but it can be converted into other types of energy. Cells use potential kinetic energy to generate stored chemical energy in the form of activated carrier molecules, which are often employed to join two molecules together in _____________ reactions. (a) oxidation (b) hydrolysis (c) condensation (d) reduction

Energy required by the cell is generated in the form of ATP. ATP is hydrolyzed to power many of the cellular processes, increasing the pool of ADP. As the relative amount of ADP molecules increases, they can bind to glycolytic enzymes, which will lead to the production of more ATP. The best way to describe this mechanism of regulation is ___________. (a) feedback inhibition. (b) oxidative phosphorylation. (c) allosteric activation. (d) substrate-level phosphorylation

Even though cellular macromolecules contain a large number of carbon and hydrogen atoms, they are not all spontaneously converted into CO2 and H2O. This absence of spontaneous combustion is due to the fact that biological molecules are relatively __________ and an input of energy is required to reach lower energy states. (a) large (b) polar (c) stable (d) unstable

Fully folded proteins typically have polar side chains on their surfaces, where electrostatic attractions and hydrogen bonds can form between the polar group on the amino acid and the polar molecules in the solvent. In contrast, some proteins have a polar side chain in their hydrophobic interior. Which of the following would not occur to help accommodate an internal, polar side chain? (a) A hydrogen bond forms between two polar side chains. (b) A hydrogen bond forms between a polar side chain and the protein backbone. (c) A hydrogen bond forms between a polar side chain and an aromatic side chain. (d) Hydrogen bonds form between polar side chains and a buried water molecule.

If the isotope 32S has 16 protons and 16 neutrons, how many protons, neutrons, and electrons will the isotope 35S have, respectively? (a) 16, 20, 15 (b) 16, 19, 15 (c) 16, 19, 16 (d) 16, 19, 17

Mitochondria contain their own genome, are able to duplicate, and actually divide on a different time line from the rest of the cell. Nevertheless, mitochondria cannot function for long when isolated from the cell because they are __________________. (a) viruses. (b) parasites. (c) endosymbionts. (d) anaerobes.

Mitochondria perform cellular respiration, a process that uses oxygen, generates carbon dioxide, and produces chemical energy for the cell. Which answer below indicates a correct pairing of material "burned" and the form of energy produced during cellular respiration? (a) fat, ADP (b) sugar, fat (c) sugar, ATP (d) fat, protein

Oxidation and reduction states are relatively easy to determine for metal ions, because there is a measurable net charge. In the case of carbon compounds, oxidation and reduction depend on the nature of polar covalent bonds. Which of the following is the best way to describe these types of bond? (a) hydrogen bonds in a nonpolar solution (b) covalent bonds in an aqueous solution (c) unequal sharing of electrons across a covalent bond (d) equal sharing of electrons across a covalent bond

Protein E can bind to two different proteins, S and I. The binding reactions are described by the following equations and values: E + S ◊ ES Keq for ES = 10 E + I ◊ EI Keq for EI = 2 Given the equilibrium constant values, which one of the following statements is true? (a) E binds I more tightly than S. (b) When S is present in excess, no I molecules will bind to E. (c) The binding energy of the ES interaction is greater than that of the EI interaction. (d) Changing an amino acid on the binding surface of I from a basic amino acid to an acidic one will probably make the free energy of association with E more negative

Proteins are important architectural and catalytic components within the cell, helping to determine its chemistry, its shape, and its ability to respond to changes in the environment. Remarkably, all of the different proteins in a cell are made from the same 20 __________. By linking them in different sequences, the cell can make protein molecules with different conformations and surface chemistries, and therefore different functions. (a) nucleotides. (b) sugars. (c) amino acids. (d) fatty acids.

Scientists learned that cell death is a normal and even important part of life by studying the development of the nematode worm C. elegans. What was the most important feature of C. elegans for the study of programmed cell death? (a) The nematode is smaller and simpler than the fruit fly. (b) 70% of C. elegans genes have homologs in humans. (c) The developmental pathway of each cell in the adult worm was known. (d) Its genome was partially sequenced.

Some prokaryotes can live by utilizing entirely inorganic materials. Which of the following inorganic molecules would you predict to be the predominant building block for fats, sugars, and proteins? (a) O 2 (b) N 2 (c) CO 2 (d) H 2

The equilibrium constant (K) for the reaction Y◊X can be expressed with respect to the concentrations of the reactant and product molecules. Which of the expressions below shows the correct relationship between K, [Y], and [X]? (a) K = [Y]/[X] (b) K = [Y] * [X] (c) K = [X]/[Y] (d) K = [X] - [Y]

The equilibrium constant for complex formation between molecules A and B will depend on their relative concentrations, as well as the rates at which the molecules associate and dissociate. The association rate will be larger than the dissociation rate when complex formation is favorable. The energy that drives this process is referred to as ___________. (a) dissociation energy. (b) association energy. (c) binding energy. (d) releasing energy

The small molecule cyclic AMP (cAMP) takes about 0.2 second to diffuse 10 µm, on average, the on one end in a cell. Suppose that cAMP is produced near plasma membrane of the cell; how long will it take for this cAMP to diffuse through the cytosol and reach the opposite end of a very large cell, on average? Assume that the cell is 200 µm in diameter. (a) 4 seconds (b) 16 seconds (c) 80 seconds (d) 200 seconds

Which pair of values best fills in the blanks in this statement: On average, eukaryotic cells are __________ times longer and have _________ times more volume than prokaryotic cells. (a) 5, 100 (b) 10, 200 (c) 10, 100 (d) 10, 1000

You have a concentrated stock solution of 10 M NaOH and want to use it to produce a 150 mL solution of 3 M NaOH. What volume of water and stock solutions will you measure out to make this new solution? (a) 135 mL of water, 15 mL of NaOH stock (b) 115 mL of water, 35 mL of NaOH stock (c) 100 mL of water, 50 mL of NaOH stock (d) 105 mL of water, 45 mL of NaOH stock

ΔG measures the change of free energy in a system as it converts reactant (Y) into product (X). When [Y] =[X], ΔG is equal to _____________. (a) ΔG° + RT (b) RT (c) ln [X]/[Y] (d) ΔG°

ΔG° indicates the change in the standard free energy as a reactant is converted to product. Given what you know about these values, which reaction below is the most favorable? (a) ADP + Pi ◊ ATP ΔG° = +7.3 kcal/mole (b) glucose 1-phosphate ◊ glucose 6-phosphate ΔG° = -1.7 kcal/mole (c) glucose + fructose ◊ sucrose ΔG° = +5.5 kcal/mole (d) glucose ◊ CO2 + H2O ΔG° = -686 kcal/mole

β Sheets can participate in the formation of amyloid ﬁbers, which are insoluble protein aggregates. What drives the formation of amyloid ﬁbers? (a) denaturation of proteins containing β sheets (b) extension of β sheets into much longer β strands (c) formation of bioﬁlms by infectious bacteria (d) β-sheet stabilization of abnormally folded proteins

In looking for functionally important nucleotide sequences is it more informative to compare the genome sequences of species M and N or species M and Q?

species M and Q

Describe a mechanism that might drive evolution toward small introns or loss of introns and could account for the evolutionary loss of introns according to the introns early hypothesis.

spontaneous deletion or selection pressure

Indicate whether the following statements are true or false. The cytoskeleton is used as a transportation grid for the efficient, directional movement of cytosolic components.

true

Indicate whether the following statements are true or false. Cells of different types can have different chemical requirements.

true

Indicate whether the following statements are true or false. Prokaryotes can adopt several different basic shapes, including spherical, rod-shaped, and spiral.

true

Indicate whether the following statements are true or false. The branchlike extensions that sprout from a single nerve cell in a mammalian brain can extend over several hundred micrometers.

true

Indicate whether the following statements are true or false. The presence of the plasma membrane can be inferred by the well-defined boundary of the cell.

true

Indicate whether the following statements are true or false. Oxygen is toxic to certain prokaryotic organisms.

true

Indicate whether the following statements are true or false. Some prokaryotes have cell walls surrounding the plasma membrane.

true

Indicate whether the following statements are true or false. Thermal energy promotes random movement of proteins, vesicles, and small molecules in the cytosol.

true

Indicate whether the following statements are true or false. Membrane components in the cell are made in the endoplasmic reticulum.

true

Indicate whether the following statements are true or false.. The Golgi apparatus is made up of a series of membrane-enclosed compartments through which materials destined for secretion must pass..

true

True or false A pseudogene is very similar to a functional gene but cannot be expressed because of mutations

true

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. Electrons are constantly moving around the nucleus of the atom, but they can move only in discrete regions. B. There is no limit to the number of electrons that can occupy the fourth electron shell. C. Atoms with unﬁlled outer electron shells are especially stable and are therefore less reactive.

true false false

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. There are four elements that constitute 99% of all the atoms found in the human body. B. Copper, zinc, and manganese are among 11 nonessential trace elements that contribute less than 0.1% of all the atoms in the human body. C. Approximately 0.9% of the atoms in the human body come from seven essential elements—Na, Mg, K, Ca, P, S, and Cl—all of which form stable ions in aqueous solution.

true false false

5-23 Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Each strand of DNA contains all the information needed to create a new double-stranded DNA molecule with the same sequence information. B. All functional DNA sequences inside a cell code for protein products. C. Gene expression is the process of duplicating genes during DNA replication. D. Gene sequences correspond exactly to the respective protein sequences producedfrom them.

true false false false

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. Electron shells ﬁll discrete regions around the nucleus of the atom and limit the number of electrons that can occupy a speciﬁc orbit. B. H, C, O, and N are the most common elements in biological molecules because they are the most stable. C. Some atoms are more stable when they lose one or two electrons, even though this means they will have a net positive charge.

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