BIO Exam 3 for REAL

True or false? A codon is a group of three bases that can specify more than one amino acid.

false

True or false? A codon is a group of three bases that can specify more than one amino acid.

False A codon is a group of three bases that can specify only one amino acid.

Which of the following best describes the significance of the TATA box in eukaryotic promoters?

It is the recognition site for a specific transcription factor.

Which of the following statements about the DNA in one of your brain cells is true?

It is the same as the DNA in one of your kidney cells.

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

It joins Okazaki fragments together

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

It joins Okazaki fragments together.

Why might a point mutation in DNA make a difference in the level of a proteins activity?

It might substitute an amino acid in the active site

What is the function of the group of amino acids on the RNA polymerase, called the rudder?

It moves template and non-template strands of DNA through channels inside the enzyme.

For a repressible operon to be transcribed, which of the following must occur?

RNA polymerase must bind to the promoter, and the repressor must be inactive.

A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in 15N medium for several generations and then transfer them to 14N medium. Which pattern in Figure 16.1 would you expect if the DNA was replicated in a conservative manner?

Tube B

In eukaryotes, the most direct result of the chromosome organization shown in Figure 19.2 is that __________.

chromosomes are coiled to occupy a much smaller volume DNA is tightly packed in the nucleus.

Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand? Select one: complementary covalently bonded identical permanently base-paired daughter strands

complementary

Which of the following occurs in prokaryotes but not in eukaryotes?

concurrent transcription and translation

A mutation that renders the product of a regulatory gene for a repressible operon nonfunctional would result in _____.

continuous transcription of the genes of the operon

What would occur if the repressor of an inducible operon mutated so that it could not bind the operator?

continuous transcription of the operon's genes

What would occur if the repressor of an inducible operon were mutated so that it could not bind the operator?

continuous transcription of the operon's genes

A mutation that inactivates a regulatory gene of a repressible operon in an E. coli cell would result in _____.

continuous transcription of the structural gene controlled by that regulator

Topoisomerase

corrects "supercoiling" ahead of replication forks by breaking, swiveling, and rejoining DNA strands • relaxes supercoiled DNA by catalyzing the controlled cleavage and rejoining of DNA. • like a comb that prevents tangling

Topoisomerase

cuts, swivels, and rejoins DNA strands ahead of the replication fork

In eukaryotic cells, translation occurs in the ________. Select one: extracellular matrix nucleus DNA cytoplasm

cytoplasm

Translation occurs in the ______________. Select one: cytoplasm nucleoplasm Golgi apparatus nucleus lysosome

cytoplasm

Translation occurs in the _____.

cytoplasm Ribosomes, the sites of translation, are found in the cytoplasm.

Translation occurs in the _____.

cytoplasm. Ribosomes, the sites of translation, are found in the cytoplasm.

A second cycle of replication produces ____ daughter DNA molecules.

four

Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?

gaps left at the 5' end of the lagging strand

Which of the following can be effective in preventing the onset of viral infection in humans?

getting vaccinated

Excision repair systems

groups of enzymes that recognize damage in DNA, excise surrounding nucleotides and repair using template strand

The first step in the replication of DNA is catalyzed by _____.

helicase

What separates the DNA strands during replication?

helicase

The first step in the replication of DNA is catalyzed by _____.

helicase • The first step of DNA replication is unwinding the DNA double helix.

The first step in the replication of DNA is catalyzed by ______.

helicase. (The first step of DNA replication is unwinding the DNA double helix.)

Attachment of acetyl groups to ______ promotes transcription.

histone tails

The letter C indicates _____.

histones

sliding clamp

holds DNA polymerase in place during single strand extension

What type of bonding is responsible for maintaining the shape of the tRNA molecule?

hydrogen bonding between base pairs

The two strands of a DNA double helix are held together by _____ that form between pairs of nitrogenous bases.

hydrogen bonds

A gene-regulation strategy that is unique to eukaryotic cells is __________.

mRNA processing Bacterial cells generally do not modify mRNAs extensively after they are synthesized.

Translation requires ____________. Select one: mRNA, tRNA, DNA, and rRNA mRNA, tRNA, and rRNA mRNA, DNA, and rRNA mRNA, tRNA, and DNA

mRNA, tRNA, and rRNA

lagging strand

made in segments, daughter strand elongates away from replication fork, multiple primers needed

DNA methylation of cytosine residues ________.

may be a mechanism of epigenetic inheritance when methylation patterns are repeated in daughter cells

In eukaryotes, what allows only certain genes to be expressed in certain types of cells?

the set of regulatory transcription factors.

Which of the following statements about DNA synthesis is true? (a) DNA polymerase adds dNTP monomers in the 3' to 5' direction. (b) Nucleotides are added in a random fashion to single-stranded DNA. (c) Primers are short sequences that allow the initiation of DNA synthesis. (d) As DNA polymerase moves along the template strand, each new nucleotide provides a 5' hydroxyl group for the next reaction to occur.

(c) Primers are short sequences that allow the initiation of DNA synthesis.

Which of the following statements about Okazaki fragments in E. coli is true? (a) They are sealed together by the action of helicase. (b) They are usually 50 to 500 bases long. (c) They are formed on the lagging strand of DNA. (d) They are synthesized in the 3' to 5' direction.

(c) They are formed on the lagging strand of DNA.

Which part of a deoxynucleoside triphosphate (dNTP) molecule provides the energy for DNA synthesis? (a) Free 3' hydroxyl (-OH) group (b) Base (c) Sugar (d) Phosphate groups

(d) Phosphate groups

Which of the following enzymes is important for relieving the tension in a helix as it unwinds during DNA synthesis? (a) Single-strand binding proteins (b) Helicase (c) Ligase (d) Topoisomerase

(d) Topoisomerase

What are the chemical components of a DNA molecule?

- nitrogenous bases. - sugars. - phosphate groups.

The process of translation, or protein synthesis, is a crucial part of the maintenance of living organisms. Proteins are constantly in use and will break down eventually, so new ones must always be available. If protein synthesis breaks down or stops, then the organism dies.

...

In a nucleotide, the nitrogenous base is attached to the sugar's _______ carbon and the phosphate group is attached to the sugar's ______ carbon.

1'; 5'

The diagram below shows two stretches of DNA in the genome of an imaginary eukaryotic cell. The top stretch of DNA includes the fantasin gene, along with its promoter and one of its enhancers. The bottom stretch of DNA includes the imaginin gene, its promoter, and one of its enhancers. The slash marks (//) indicate that more than 1,000 nucleotides separate the promoter and enhancer of each gene.

1). Control elements C, D, and E are distal control elements for the imaginin gene. 2). The fantasin gene will be transcribed at a high level when activators specific for control elements A, B, and C are present in the cell. 3). Both the fantasin gene and the imaginin gene will be transcribed at high levels when activators specific for control elements A, B, C, D, and E are present in the cell.

In all organisms, certain genes are expressed at any given time while other genes are not. Both prokaryotes and eukaryotes regulate gene expression at the transcription stage. However, the greater complexity of eukaryotic cells makes it possible for gene expression to be regulated at many other stages as well. The diagram below shows different stages at which gene expression may be regulated in eukaryotes.

1).DNA is not transcribed when chromatin is packaged tightly in a condensed form. 2). Methylation of histone tails in chromatin can promote condensation of the chromatin. 3). Acetylation of histone tails in chromatin allows access to DNA for transcription. 4). Some forms of chromatin modification can be passed on to future generations of cells. 5). Acetylation of histone tails is a reversible process.

Triplet

3 letter code in DNA

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is _____.

3' UCA 5'

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'.

RNA polymerase moves in which direction along the DNA?

3' to 5' along the template strand

Put the following events of transcription in chronological order. 1. Sigma binds to the promoter region. 2. The double helix of DNA is unwound, breaking hydrogen bonds between complementary strands. 3. Sigma binds to RNA polymerase. 4. Sigma is released. 5. Transcription begins.

3, 1, 2, 5, 4

Hershey and Chase used _____ to radioactively label the T2 phage's proteins.

35S.

which direction does does DNA replicate

5' --> 3'

Which of the following, if missing, would usually prevent translation from starting in eukaryotes? Select one: exon 5' cap or AUG codon AUG codon 5' cap exon, 5' cap, or AUG codon

5' cap or AUG codon

Nucleic acids are assembled in the ___ direction

5' to 3' (new nucleotides are added to the 3' end of a growing polynucleotide)

The direction of synthesis of an RNA transcript is ___________. Select one: 2' to 4' 1' to 5' 5' to 3' 1' to 3' 3' to 5'

5' to 3' Nucleotides are added to the 3' end of RNA.

During RNA processing a(n) _____ is added to the 3' end of the RNA.

5' untranslated region A poly-A tail is added to the 3' end of the RNA.

The direction of synthesis of an RNA transcript is _____.

5' —> 3'. Nucleotides are added to the 3' end of RNA.

In comparing DNA replication with RNA transcription in the same eukaryotic cell, only DNA replication _____. a. incorporates the entire template molecule in the product b. makes a new molecule from its 5' end to its 3' end c. uses RNA polymerase d. occurs in the nucleus of the cell

A

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?

A gene from an organism can theoretically be expressed by any other organism

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?

A gene from an organism can theoretically be expressed by any other organism.

Which of the following statements about mutations is false? Select one: Addition and deletion mutations disrupt the primary structure of proteins. A deletion mutation results in the loss of a base in the DNA sequence. An addition mutation results in an added base in the DNA sequence A knock-out mutation results in a total absence of the mutated protein.

A knock-out mutation results in a total absence of the mutated protein.

Which of the following statements about mutations is false?

A knock-out mutation results in a total absence of the mutated protein. A knock-out mutation refers to the loss of a protein's function but not necessarily to its complete absence.

An example of post-translational control is:

A protein is phosphorylated on a particular amino acid. This is a very common regulatory mechanism for altering protein activity.

How does the arrival of a termination codon at the A site trigger the end of protein synthesis?

A protein release factor binds in the A site and releases the polypeptide from the final tRNA to which it is bound. After polypeptide release the ribosome dissociates.

How does termination of translation take place?

A stop codon is reached

6) Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

A) 8%

Which one of the following structures, if missing, would usually prevent translation from starting? A) AUG codon B) 5′ cap C) poly-A tail D) exon

A) AUG codon

35) Which of the following sets of materials are required by both eukaryotes and prokaryotes for replication?

A) double-stranded DNA, four kinds of dNTPs, primers, origins

57) The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?

A) nuclease, DNA polymerase, DNA ligase

42) Which of the following represents the order of increasingly higher levels of organization of chromatin?

A) nucleosome, 30-nm chromatin fiber, looped domain

8) It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following?

A) sequence of bases

What allows for the more complex morphology of humans relative to those of simple invertebrates such as nematodes?

Alternative RNA splicing

primase

An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template.

DNA methylation and histone acetylation are examples of _____. a. chromosomal rearrangements b. epigenetic phenomena c. karyotypes d. translocation e. genetic mutation

B

52) In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?

B) A + G = C + T

45) A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in 15N medium for several generations and then transfer them to 14N medium. Which pattern in the figure above would you expect if the DNA was replicated in a conservative manner?

B) B

Why is RNA interference aptly named?

Both the miRNA that does the interfering and the mRNA that is destroyed are RNA.

An example of a basal transcription factor is _____. a. a silencer-binding transcription factor b. a promoter-proximal-binding transcription factor c. the TATA-binding protein d. RNA polymerase e. an enhancer-binding transcription factor

C

An experimenter has altered the 3'end of the tRNA corresponding to the amino acid methionine in such a way as to remove the 3' bases AC. Which of the following hypotheses describes the most likely result? a. The aminoacyl-tRNA synthetase will not be formed. b. The anticodon will not bind with the mRNA codon. c. The amino acid methionine will not become covalently bound. d. tRNA will not form a cloverleaf.

C

Which of these directly bind(s) to the promoter?

C and D

27) What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

C) It joins Okazaki fragments together.

Once researchers identified DNA as the molecule responsible for transmitting heritable traits, they asked how information was transferred from the DNA in the nucleus to the site of protein synthesis in the cytoplasm. Which of the following statements correctly describes the mechanism of information transfer in eukaryotes that accomplishes this task? A) Histone proteins in the chromosomes transfer information from the nucleus to the ribosome, where protein synthesis takes place. B) Transfer RNA takes information from DNA directly to a ribosome, where protein synthesis takes place. C) Messenger RNA is transcribed from a single gene and transfers information from the DNA in the nucleus to the cytoplasm, where protein synthesis takes place. D) DNA from a single gene is replicated and transferred to the cytoplasm, where it serves as a template for protein synthesis.

C) Messenger RNA is transcribed from a single gene and transfers information from the DNA in the nucleus to the cytoplasm, where protein synthesis takes place.

Which of the following statements best describes the termination of transcription in prokaryotes? A) Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome. B) RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript and cut it free from the polymerase. C) RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript. D) RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA.

C) RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.

During elongation, RNA polymerase has three prominent channels, or grooves. These channels provide sites for all of the following, except _____. A) a site for the double-stranded DNA molecule B) a site for the entry of ribonucleoside triphosphates C) a site for the exit of the diphosphates removed from the nucleotide triphosphates D) a site for the growing RNA strand

C) a site for the exit of the diphosphates removed from the nucleotide triphosphates

54) In a nucleosome, the DNA is wrapped around

C) histones.

22) What is the function of DNA polymerase III?

C) to add nucleotides to the 3' end of a growing DNA strand

Which of these is (are) pyrimidines?

C,D, and E. (Pyrimidines are single-ring structures.)

Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare?

Codons are a nearly universal language among all organisms

Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand?

Complementary Because the template strand determines the nucleotides to be added to the RNA strand, using the same complementarity rules of the DNA, they will be complementary to each other.

In comparing DNA replication with RNA transcription in the same eukaryotic cell, only DNA replication _____. a. uses RNA polymerase b. occurs in the nucleus of the cell c. makes a new molecule from its 5' end to its 3' end d. incorporates the entire template molecule in the product

D

The following question refers to this table of codons. Which of the following sequences of nucleotides are possible in the template strand of DNA that would code for the polypeptide sequence Phe-Leu-Ile-Val? A) 5′-AUG-CTG-CAG-TAT-3′ B) 3′-AAA-AAT-ATA-ACA-5′ C) 5′-TTG-CTA-CAG-TAG-3′ D) 3′-AAA-GAA-TAA-CAA-5′

D) 3′-AAA-GAA-TAA-CAA-5′

A particular triplet of bases in the template strand of DNA is 5′-AGT-3′. What would be the corresponding codon for the mRNA that is transcribed? A) 3′-UGA-5′ B) 5′-TCA-3′ C) 3′-UCA-5′ D) 3′-ACU-5′

D) 3′-ACU-5′

19) At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork:

D) 5' A C G U U A G G 3'

17) The enzyme telomerase solves the problem of replication at the ends of linear chromosomes by which method?

D) adding numerous short DNA sequences such as TTAGGG, which form a hairpin turn

In the diagram below, the two blue strands represent _____.

DNA

What are the steps (in the correct order) that link a change in the base sequence of a gene to a change in the phenotype of an organism like a mouse or a human? Select one: DNA --> Protein --> RNA Protein --> RNA --> DNA RNA --> DNA --> Protein DNA --> RNA --> Protein

DNA --> RNA --> Protein

Altering patterns of gene expression in prokaryotes would most likely serve an organism's survival by _____. a. allowing young organisms to respond differently than more mature organisms b. allowing each gene to be expressed an equal number of times c. organizing gene expression, so that genes are expressed in a given order d. allowing environmental changes to alter a prokaryote's genome e. allowing an organism to adjust to changes in environmental conditions

E

If you were to observe the activity of methylated DNA, you would expect it to _____. a. be replicating nearly continuously b. be unwinding in preparation for protein synthesis c. be very actively transcribed and translated d. induce protein synthesis by not allowing repressors to bind to it e. have turned off or slowed down the process of transcription

E

34) Which of the enzymes synthesizes short segments of RNA?

E) V

2) How do we describe transformation in bacteria?

E) assimilation of external DNA into a cell

21) To repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?

E) endonuclease, DNA polymerase I, DNA ligase

18) The DNA of telomeres has been found to be highly conserved throughout the evolution of eukaryotes. What does this most probably reflect?

E) that the critical function of telomeres must be maintained

True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated. Select one: True False

False

The operon model for the control of gene expression was discovered by which of the following?

Francois Jacob and Jacques Monod

Which of these correctly illustrates the pairing of DNA and RNA nucleotides?

GTTACG CAAUGC

Which tRNA anticodon(s) could decode the mRNA codon CAG (recall that codons are always written in the 5'—>3' direction and anticodons are written in the 3'—>5' direction)?

GUC

One way that gene regulation in eukaryotic and prokaryotic cells is similar is:

In both types of cell, the primary mechanism to regulate gene expression is at the level of transcriptional regulation.

A mutation that results in premature termination of translation _____.

Is a nonsense mutation

What is the function of the ACC sequence at the 3' end? (image: Hairpin structure of RNA with "AGU" towards the bottom of the pin and "ACC" at the top)

It attaches to the amino acid.

What is the function of the release factor (RF)?

It binds to the stop codon in the A site in place of a tRNA.

What happens to RNA polymerase II after it has completed transcription of a gene? Select one: It is degraded. It begins transcribing the next gene on the chromosome. It is free to bind to another promoter and begin transcription. It joins with another RNA polymerase to carry out transcription.

It is free to bind to another promoter and begin transcription.

What happens to RNA polymerase II after it has completed transcription of a gene?

It is free to bind to another promoter and begin transcription. The enzyme is free to transcribe other genes in the cell.

During initiation of translation, the initiator tRNA is placed in the P site leaving the A site open. Which of the following statements does NOT explain why it is important to leave site A available? Select one: It is necessary because codons in the mRNA are read in the A site. It is necessary for the proper assembly of the ribosome. It is necessary because new peptide bonds form between the amino acids of the tRNA in P and the incoming amino-acyl tRNA in site A. It is necessary to leave room for the second amino-acyl tRNA to occupy site A.

It is necessary for the proper assembly of the ribosome.

What is the function of RNA polymerase?

It unwinds the double helix and adds nucleotides to a growing strand of RNA. RNA polymerase has several functions in transcription, including unwinding the DNA double helix and adding RNA nucleotides.

What does it mean when we say the genetic code is redundant?

More than one codon can specify the addition of the same amino acid.

Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)?

One addition and one deletion mutation. This combination results in no net change in the number of bases, so the reading frame would eventually be restored.

How could alternative splicing allow two different species with the same number of genes to produce vastly different numbers of proteins?

One species could produce many different mRNA from each of their genes while another only produces one or a few.

DNA does not store the information to synthesize which of the following?

Organelles Synthesis of organelles is not directly coded in the DNA.

The initiator tRNA attaches at the ribosome's _____ site. Select one: P Q translocation A E

P

Which of the following processes is an example of a post-translational modification? Select one: Peptide bond formation Initiation Phosphorylation Elongation

Phosphorylation

Which of the following processes is an example of a post-translational modification?

Phosphorylation. Enzymes can phosphorylate proteins to alter their activity.

mRNA is smaller than the length of the DNA that codes for it because _____.

Post-transcriptional modification removes the introns

Which of the following enzymes creates a primer for DNA polymerase

Primase

Enzyme complexes that break down protein are called _____.

Proteasomes

The enzyme complex associated with DNA in the figure is

RNA Polymerase

In 2009, a flu pandemic was believed to have originated when viral transmission occurred from pig to human, thereby earning the designation, "swine flu." Although pigs are thought to have been the breeding ground for the 2009 virus, sequences from bird, pig, and human viruses were all found within this newly identified virus. What is the most likely explanation of why this virus contained sequences from bird, pig, and human viruses?

Related viruses can undergo genetic recombination if the RNA genomes mix and match during viral assembly.

Where does translation take place?

Ribosome

Where does translation take place?

Ribosome Translation, or protein synthesis, occurs at the ribosome.

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

Selected Answer: 8%

In an analysis of the nucleotide composition of DNA, which of the following will be found?

Selected Answer: A + C = G + T

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

Selected Answer: DNA in both daughter cells would be radioactive.

In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the 5' → 3' direction?

Selected Answer: DNA polymerase III

How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes? It adds a single 5' cap structure that resists degradation by nucleases. It causes specific double-strand DNA breaks that result in blunt ends on both strands. It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity. It adds numerous GC pairs, which resist hydrolysis and maintain chromosome integrity.

Selected Answer: It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity.

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication? It synthesizes RNA nucleotides to make a primer. It joins Okazaki fragments together. It unwinds the parental double helix. It stabilizes the unwound parental DNA.

Selected Answer: It joins Okazaki fragments together.

Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons? Prokaryotic chromosomes have histones, whereas eukaryotic chromosomes do not. Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many. The rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes. Prokaryotes produce Okazaki fragments during DNA replication, but eukaryotes do not.

Selected Answer: Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.

If a cell were unable to produce histone proteins, which of the following would be a likely effect?

Selected Answer: The cell's DNA couldn't be packed into its nucleus

Which of the following would you expect of a eukaryote lacking telomerase? a high probability of somatic cells becoming cancerous an inability to produce Okazaki fragments an inability to repair thymine dimers a reduction in chromosome length in gametes

Selected Answer: a reduction in chromosome length in gametes

If RNA polymerase is missing _____ then transcription initiation would not occur but elongation could

Sigma

What are their differences?

Sigma is part of the RNA polymerase holoenzyme, while the general transcription complex recruits RNA polymerase to the promoter.

What is the function of the sigma subunit of RNA polymerase in bacterial transcription?

Sigma is the portion of the enzyme that recognizes specific sequences in the promoter. Without sigma, RNA polymerase can bind to any sequence of DNA.

Telomere shortening puts a limit on the number of times a cell can divide. Research has shown that telomerase can extend the life span of cultured human cells. How might adding telomerase affect cellular aging?

Telomerase eliminates telomere shortening and retards aging.

What is meant by the description "antiparallel" regarding the strands that make up DNA?

The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

The ribosome-binding site of prokaryotes is also known as _____.

The Shine-Dalgarno sequence

What is the start codon? Select one: a. an anticodon b. a robozyme c. AUG d. CGC

The answer is: AUG.

Ribosomes can attach to prokaryotic messenger RNA________. Select one: a. Once the primary transcript has been released from RNA polymerase. b. Before transcription is complete c. Once replication is complete d. once post-transcriptional modification is complete.

The answer is: Before transcription is complete.

(x)What molecule is responsible for the catalytic activity in the spliceosomes that are involved in removal of introns? Select one: a. Proteins of the spliceosome b. Ribozymes c. Autocatalysis by introns d. RNA polymerase

The answer is: Ribozymes.

What molecule/feature ensures that the correct amino acid is added with reading of a specific codon during translation?

The anticodon of a properly formed aminoacyl tRNA

If a cell were unable to produce histone proteins, which of the following would be a likely effect?

The cell's DNA couldn't be packed into its nucleus.

What is the difference between the core promoter and promoter-proximal regulatory elements?

The core promoter is the site for binding of proteins required for transcribing all genes, such as TATA-binding protein and RNA polymerase, but the promoter-proximal elements are unique to sets of genes that are regulated together.

Erwin Chargaff observed that the proportions of adenine (A) and thymine (T) bases were always equal, as were the proportion of guanine (G) and cytosine (C). Chargaff's observation suggests what?

The data suggest that A would always pair with T and G would always pair with C in a DNA molecule.

Which of the following steps occurs last in the initiation phase of translation?

The large ribosomal subunit joins the complex. This step occurs after the 5' mRNA is bound by the ribosome and the start codon is bound by an aminoacyl tRNA.

Which of the following steps occurs last in the initiation phase of translation?

The large ribosomal subunit joins the complex. This step occurs after the 5' mRNA is bound by the ribosome and the start codon is bound by an aminoacyl tRNA.

What is the difference between the leading strand and the lagging strand in DNA replication?

The leading strand is synthesized continuously in the 5' → 3' direction, while the lagging strand is synthesized discontinuously in the 5' → 3' direction.

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed its 5' cap and poly-A tail. Which of the following would you expect her to find?

The molecule is digested by enzymes because it is not protected at the 5' end.

Which statement is most accurate concerning how gene expression in eukaryotes compares with that in bacteria?

The number of proteins that controls transcription is much greater in eukaryotes.

There should be a strong positive correlation between the rate of protein synthesis and _____.

The number of ribosomes

Which molecule or reaction supplies the energy for polymerization of nucleotides in the process of transcription?

The phosphate bonds in the nucleotide triphosphates that serve as substrates

Which of the following is an example of positive regulation of gene expression in E. coli?

The role of cyclic AMP in regulation of the lac operon

How is translation initiated?

The small ribosomal subunit binds to the mRNA. The tRNA bearing methionine binds to the start codon. The large ribosomal subunit binds to the small one. The start codon signals the start of translation. All of these processes occur at the initiation of translation.

Griffith's experiments with S. pneumoniae were significant because they showed that traits could be transferred from one organism to another. What else did he find that was significant?

The transferred traits were heritable.

How are RNA hairpin turns related to termination?

The turns are formed from complementary base pairing and cause separation of the RNA transcript and RNA polymerase.

DNase is an enzyme that catalyzes the hydrolysis of the covalent bonds that join nucleotides together. What would first happen to DNA molecules treated with DNase?

The two strands of the double helix would separate

Viruses use the host's machinery to make copies of themselves. However, some human viruses require a type of replication that humans do not normally have. For example, humans normally do not have the ability to convert RNA into DNA. How can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires?

The viral genome codes for specialized enzymes not in the host.

What are their differences?

There usually is more than one promoter-proximal element in the cell, but only one lac operon.

What is the reaction catalyzed by aminoacyl-tRNA synthetases?

These enzymes catalyze formation of the bonds between the tRNA and the appropriate amino acids. This is known as "charging" a tRNA.

Which of the following supports the argument that viruses are nonliving?

They are not cellular.

David Pribnow studied the base sequences of promoters in bacteria and bacterial viruses. He found two conserved regions in these promoters (the -10 box and the -35 box). What is the function of these two regions of the promoter?

They bind the sigma subunit that is associated with RNA polymerase.

In a DNA double helix an adenine of one strand always pairs with a(n) ______ of the complementary strand, and a guanine of one strand pairs with a(n) ________ of the complementary strand.

Thymine; cytosine

Which of the following enzymes is important for relieving the tension in a helix as it unwinds during DNA synthesis?

Topoisomerase

Which of the following enzymes is important for relieving the tension in a helix as it unwinds during DNA synthesis?

Topoisomerase • This enzyme untwists the coils that occur in the DNA as it is being unwound into a single-stranded template.

What is the process called that converts the genetic information stored in DNA to an RNA copy?

Transcription DNA is transcribed to give an RNA copy.

Eukaryotes have three nuclear RNA polymerases. The primary function of RNA polymerase II is _____.

Transcription of protein-coding genes

Indicate at which step of the replication-transcription-translation process each type of RNA first plays a role.

Transcription/RNA processing: mRNA Translation: tRNA, rRNA During replication, a faithful copy of a DNA molecule is made. During transcription, the DNA "message" is copied onto a molecule of mRNA. During translation, the information carried in the mRNA is transferred to molecules of tRNA to build a protein on the ribosomes.

MicroRNAs control gene expression at the level of _______.

Translation

The letter A indicates _____.

a DNA double helix

Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?

a base-pair deletion

A mutation that results in premature termination of translation is _____.

a nonsense mutation

What is responsible for termination of transcription in eukaryotic protein-coding genes? Select one: a termination loop composed of guanine a polyadenylation, or poly(A), signal three nonsense mutations in sequence a sigma factor a portion of the polymerase holoenzyme

a polyadenylation, or poly(A), signal

anticodons

a sequence of three nucleotides forming a unit of genetic code in a tRNA molecule, corresponding to a complementary codon in messenger RNA.

Which of the following statements describes a eukaryotic chromosome?

a single linear molecule of double-stranded DNA plus proteins

Altering patterns of gene expression in prokaryotes would most likely serve an organism's survival by _____.

allowing an organism to adjust to changes in environmental conditions

Polypeptides are assembled from _______________. Select one: amino acids hexoses proteins glycerol nucelotides

amino acids

Polypeptides are assembled from _____.

amino acids Proteins are composed of amino acid monomers.

Amino acids are attached to tRNA by enzymes called

aminoacyl-tRNA synthetase

What enzyme catalyzes the attachment of an amino acid to tRNA? Select one: rubisco aminoacyl-tRNA synthetase RNA polymerase dextrinase nuclease

aminoacyl-tRNA synthetase

When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate?

an assembled ribosome with a polypeptide attached to the tRNA in the P site

exonuclease

an enzyme that removes successive nucleotides from the end of a polynucleotide molecule

A eukaryotic gene is typically associated with all of the following except __________.

an operator

Inducible enzymes ______.

are produced when a molecule inactivates a repressor protein

Okazaki Fragments

are the short sections of DNA that are synthesized on the lagging strand of the replicating DNA

Compare and contrast promoter-proximal elements and the operator of the lac operon. What do they have in common?

both are regulatory sites in DNA located close to the promoter

Alternative RNA splicing

can allow the production of proteins of different sizes and functions from a single mRNA.

Predict how a drug that inhibits histone deacetylase will alter gene expression.

chromatin would stay decondensed; transcription would be prolonged; amount of protein would increase

In eukaryotes, the most direct result of the chromosome organization shown in Figure 19.2 is that __________.

chromosomes are coiled to occupy a much smaller volume

Primase

creates short RNA primers, initiating DNA synthesis on both template strands

What are pyrimidines?

cytosine, thymine, uracil

After replication is complete, the new DNAs, called _________, are identical to each other.

daughter DNA

leading strand

daughter strand elongates toward replication fork, only one primer needed, and made continuously

Nirenberg and Mattaei (1961)

deciphered genetic code

Treatment of a decondensed region of DNA with DNase I would result in _______.

degraded DNA This assay is often used to determine whether a promoter lies in an area that is tightly condensed, or decondensed.

After DNA replication is completed ______

each new DNA double helix consists of one old DNA strand and one new DNA strand

After DNA replication is completed, _____.

each new DNA double helix consists of one old DNA strand and one new DNA strand

A frameshift mutation could result from

either an insertion or a deletion of a base.

To repair a thymine dimmer by nucleotide excision repair, in which order do the necessary enzymes act?

endonuclease, DNA polymerase I, DNA ligase

Telomerase

enzyme that REPLICATES TELOMERES but its only active in meiotic cells forming gametes • Its important that you pass on all the genetic material you can to offspring otherwise they would be born old if they were passed down DNA with degraded telomeres

RNA polymerase

enzyme that builds mRNA single strand complementary to DNA sequence

The control of gene expression is more complex in eukaryotic cells than prokaryotic cells because ___________.

eukaryotic DNA is packaged with proteins in an elaborate complex

The RNA segments joined to one another by spliceosomes are _____. Select one: snRNPs exons caps introns tails

exons

_______________ of translation always happens at the start codon of the mRNA.

initiation

You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent

leading strands and Okazaki fragments.

Short segments of newly synthesized DNA are joined into a continuous strand by _____.

ligase

Short segments of newly synthesized DNA are joined into a continuous strand by _________.

ligase

Which of the following covalently connects segments of DNA? primase DNA polymerase III DNA polymerase I ligase helicase

ligase

What is this an image of? The figure shows a thread. It is undulating. From this undulating thread, larger waves are formed. (Thinner purple scribbles: Part E)

loops

The expression of the trp operon occurs when tryptophan levels are ___

low

According to the central dogma, what molecule should go in the blank? DNA → _____ → Proteins

mRNA

What amino acid sequence will be generated, based on the following mRNA codon sequence? 5' AUG-UCU-UCG-UUA-UCC-UUG 3'

met-ser-ser-leu-ser-leu

What are prions?

misfolded versions of normal protein that can cause disease

During RNA processing a(n) _____ is added to the 5' end of the RNA. Select one: 3' untranslated region 5' untranslated region coding segment a long string of adenine nucleotides modified guanine nucleotide

modified guanine nucleotide

As a result of splicing, most protein-coding genes can encode ______ protein. Select one: exactly one fewer than one more than one differently spliced

more than one

As a result of splicing, most protein-coding genes can encode ______ protein.

more than one This allows one gene to code for different mRNAs.

This is an image of an ______

nucleotide. (nucleotides are composed of pentose sugar, a nitrogenous base, and a phosphate group).

Semiconservative replication involves a template. What is the template?

one strand of the DNA molecule

A DNA replication bubble forms at a specific sequence of bases called the ___________.

origin of replication

Why do loss of function mutations in p53 often lead to mutations in other genes?

p53 normally functions as a tumor suppressor to stop the cell cycle after DNA damage occurs.

This is an image of a _____.

phage. (This is a T2 phage, a type of phage that infects E. coli.)

The letter A indicates a ________.

phosphate group. (phosphate groups contain phosphorus)

Which part of a deoxynucleoside triphosphate (dNTP) molecule provides the energy for DNA synthesis?

phosphate groups

Which part of a deoxynucleoside triphosphate (dNTP) molecule provides the energy for DNA synthesis?

phosphate groups • The potential energy stored in the bonds of the phosphates provides the energy for DNA synthesis.

Which of the following synthesizes short segments of RNA?

primase

Gene expression

process of converting archived info into molecules that actually do things

Protein-phosphorylating enzymes' role in the regulation of gene expression involves _____.

protein activation

The nuclear membrane's role in the regulation of gene expression involves _____.

regulating the transport of mRNA to the cytoplasm

What is the function of topoisomerase?

relieving strain in the DNA ahead of the replication fork

DNA polymerase I

removes the RNA primer and replaces it with DNA nucleotides

DNA Polymerase I

removes the RNA primers and replaces them with DNA nucleotides

During DNA replication, an open section of DNA, in which a DNA Polymerase can replicate DNA, is called a

replication fork

Spliceosomes are composed of _____.

small RNAs and proteins. Spliceosomes are complexes composed of small RNAs and proteins.

Spliceosomes are composed of _____.

snRNPs and other proteins These are the component of spliceosomes.

You can tell that this is an image of a DNA nucleotide and not an RNA nucleotide because you see a _______.

sugar with two, and not three, oxygen atoms. (DNA nucleotides are composed of deoxyribose sugars, whereas RNA nucleotides are composed of ribose sugars)

both strands

synthesized 5 to 3

What is a telomere?

the ends of linear chromosomes

The leading and the lagging strands differ in that ________.

the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction

There should be a strong positive correlation between the rate of protein synthesis and _____. Select one: the quantity of DNA polymerase the number of ribosomes the quantity of RNA polymerase the size of mRNA

the number of ribosomes

Mendel and Morgan did not know about the structure of DNA; however, which of the following of their contributions was (were) necessary to Watson and Crick?

the particulate nature of the hereditary material

In the diagram below, the green unit represents _____.

the promoter. The promoter is the region of DNA at which the process of transcription begins.

A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain.

three ... amino acid Three nucleotide bases make up a codon and specify which amino acid comes next in the sequence.

Codon

three-nucleotide sequence on mRNA that codes for a single amino acid

In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.

thymine ... cytosine

Which of these nitrogenous bases is found in DNA but not in RNA? a. adenine b. cytosine c. guanine d. uracil e. thymine

thymine. (DNA contains thymine; RNA does not.)

In a DNA double helix an adenine of one strand always pairs with a(n) ______ of the complementary strand, and a guanine of one strand always pairs with a(n) ________ of the complementary strand.

thymine; cytosine. (this is referred to as specific base pairing)

What is the function of DNA polymerase III?

to add nucleotides to the end of a growing DNA strand

The functioning of enhancers is an example of ______.

transciptional control of gene expression

What is the process called that converts the genetic information stored in DNA to an RNA copy? Select one: Translation Translocation Replication Transcription

transcription

The process, performed by the ribosome, of reading mRNA and synthesizing a protein is called

translation

One cycle of replication will produce ___daughter DNA molecules, each with one parental strand and one newly synthesized strand.

two

Viruses _____.

use the host cell to copy themselves and make viral proteins

Meselson and Stahl (1958)

• Determined method of DNA replication • DNA replication is semiconservative (half old DNA and half new)

Watson and Crick (1953)

• Discovered double helix structure of DNA • Bases can pair to replicate

what are the characteristics of the genetic code?

• Redundant (amino acid —> codon) • Unambiguous (single codon = 1 amino acid) • Non overlapping • Nearly universal (with few exceptions) • Conservative (codons differ in 3rd base when coding for amino acids)

what are the causes of DNA damage?

• Spontaneous breakage (nobody knows why) • Radiation • Free radicals • Chemicals

Hershey and Chase (1952)

• is genetic material protein or DNA ? • Used a bacteriophage (virus that attacks bacteria) to provide evidence that DNA was a molecule of heredity

Which nucleic acid is translated to make a protein?

mRNA mRNA is the message that is translated to make a protein

In the process of transcription ______

mRNA is synthesized

A gene-regulation strategy that is unique to eukaryotic cells is __________.

mRNA processing

Start codon

AUG (codes for methionine)

_____ bind(s) to DNA enhancer regions.

Activators

True or false? Single-stranded DNA molecules are said to be antiparallel when they are lined up next to each other but oriented in opposite directions. (a) True (b) False

(a) True

What catalyzes DNA synthesis? (a) Replication fork (b) Primer (c) DNA polymerase (d) dNTPs

(c) DNA polymerase

Which of the following enzymes creates a primer for DNA polymerase? (a) Ligase (b) Topoisomerase (c) Primase (d) Helicase

(c) Primase

What did the structure of DNA's double helix suggest about DNA's properties?

- DNA can change. Errors in copying can result in changes in the DNA sequence that could be inherited by future generations. -DNA can be replicated by making complementary copies of each strand. -DNA stores genetic information in the sequence of its bases.

In the 1950s, when Watson and Crick were working on their model of DNA, which concepts were well accepted by the scientific community?

- Genes are located on chromosomes. - Chromosomes are made up of protein and nucleic acid. - Chromosomes are found in the nucleus.

Put the following events of elongation in prokaryotic translation in chronological order. 1. Binding of mRNA with small ribosomal subunit 2. Recognition of initiation codon 3. Complementary base pairing between initiator codon and anticodon of initiator tRNA 4. Base pairing of the mRNA codon following the initiator codon with its complementary tRNA 5. Attachment of the large subunit

1, 2, 3, 5, 4

Put the steps of DNA replication in chronological order.

1. Hydrogen bonds between base pairs of antiparallel strands are broken. 2. Single-stranded binding proteins attach to DNA strands. 3. Primase binds to the site of origin. 4. An RNA primer is created. 5. DNA polymerase binds to the template strand.

If the sequence in the coding strand of DNA for a particular amino acid is 5'AGT3', then the anticodon on the corresponding tRNA would be ________. Select one: 5'AGU3' 5'TCA3' 5'UCA3' 5'ACU3'

5'AGU3'

Use Figure 16.1 to answer the following question. In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" nitrogen (15N) and then transferred them to a medium containing 14N. Which of the results in Figure 16.1 would be expected after one round of DNA replication in the presence of 14N?

14N-15N hybrid DNA

Beadle and Tatum (1941)

1st to use "knock out" genes (if you want to know how a gene works, you mutate it and see what happens when it doesn't work) • Used metabolic pathway using bread mold • Proposed "one gene, one enzyme" hypothesis

Put the following steps of DNA replication in chronological order. 1. Single-stranded binding proteins attach to DNA strands. 2. Hydrogen bonds between base pairs of antiparallel strands are broken. 3. Primase binds to the site of origin. 4. DNA polymerase binds to the template strand. 5. An RNA primer is created.

2, 1, 3, 5, 4

A typical human cell expresses about what portion of its protein-coding genes at any given time?

20%

Use this representation to answer the following question. DNA template strand 5' ___________________________ 3' DNA nontemplate strand 3' ___________________________ 5' Given the locally unwound double strand above, in which direction does the RNA polymerase move while transcribing DNA? Select one: 5' → 3' along the double-stranded DNA 5' → 3' along the template DNA strand 3' → 5' along the template DNA strand 3' → 5' along the nontemplate DNA strand 5' → 3' along the nontemplate DNA strand

3' → 5' along the template DNA strand

Activator proteins in eukaryotes usually have a domain that binds to DNA and other activation domains that often bind to _____. a. other regulatory proteins b. protein-based hormones c. DNA polymerases d. ATP e. tRNA

A

Activator proteins in eukaryotes usually have a domain that binds to DNA and other activation domains that often bind to _____. a. other regulatory proteins b. ATP c. tRNA d. protein-based hormones e. DNA polymerases

A

During elongation, which site in the ribosome represents the location where a codon is being read? a. A site b. P site c. E site d. the small ribosomal subunit

A

How does termination of translation take place? a. A stop codon is reached. b. The poly-A tail is reached. c. The 5' cap is reached. d. The end of the mRNA molecule is reached.

A

In a nucleosome, the DNA is wrapped around _____. a. histones b. polymerase molecules c. ribosomes d. satellite DNA e. a thymine dimer

A

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed its 5' cap and poly-A tail. Which of the following would you expect her to find? a. The molecule is digested by enzymes because it is not protected at the 5' end. b. The mRNA is quickly converted into a ribosomal subunit. c. The cell adds a new poly-A tail to the mRNA. d. The mRNA attaches to a ribosome and is translated, but more slowly.

A

Muscle cells differ from nerve cells mainly because they _____. a. express different genes b. have unique ribosomes c. have different chromosomes d. contain different genes e. use different genetic codes

A

Regulatory transcription factors _____. a. influence the assembly of the basal transcription complex b. influence the degree of unwinding of DNA at the promoter c. open the two strands of DNA so that RNA polymerase can begin transcription d. influence the binding of sigma factor to DNA

A

Where would RNA polymerase attach?

A

Which of the following levels of gene expression allows the most rapid response to environmental change? a. post-translational control b. transcriptional control c. translational control

A

Which of the following mutations is most likely to cause a phenotypic change? a. a single nucleotide deletion in an exon coding for an active site b. a nucleotide substitution in an exon coding for a transmembrane domain c. a duplication of all or most introns d. a large inversion whose ends are each in the same region between genes e. a frameshift mutation one codon away from the end of the nontemplate strand

A

Which of these indicates an enhancer region?

A

In an analysis of the nucleotide composition of DNA, which of the following will be found?

A + C = G + T

Which of the following would you expect to find as part of the receptor for a steroid hormone?

A domain that binds to DNA and domains that bind proteins.

Step one of lagging strand synthesis

A new fragment begins with DNA polymerase III binding to the 3' end of the most recently produced RNA primer, primer B in this case, which is closest to the replication fork. DNA pol III then adds DNA nucleotides in the 5' to 3' direction until it encounters the previous RNA primer, primer A.

You have affixed a chromosome to a microscope slide. Which of the following would not make a good radioactively labeled probe to determine the presence of a particular gene on the chromosome?

A portion of the amino acid sequence of the gene's protein product.

Which of the following contradicts the one-gene, one-enzyme hypothesis? Select one: Sickle cell anemia results in defective hemoglobin. A single antibody gene can code for different related proteins, depending on the splicing that takes place post-transcriptionally. A mutation in a single gene can result in a defective protein. Alkaptonuria results when individuals lack a single enzyme involved in the catalysis of homogentisic acid.

A single antibody gene can code for different related proteins, depending on the splicing that takes place post-transcriptionally.

Transcription begins at a promoter. What is a promoter? Select one: The same as a start codon Part of the RNA molecule itself A site in DNA that recruits the RNA Polymerase A site found on the RNA polymerase

A site in DNA that recruits the RNA Polymerase

Transcription begins at a promoter. What is a promoter?

A site in DNA that recruits the RNA Polymerase This is the site where the RNA polymerase must bind to initiate transcription.

Rank the following one-base point mutations with respect to their likelihood of affecting the structure of the corresponding polypeptide (from most likely to least likely). 1. insertion mutation deep within an intron 2. substitution mutation at the third position of a codon in an exon 3. substitution mutation at the second position of a codon in an exon 4. deletion mutation within the first exon of the gene A) 4, 3, 2, 1 B) 2, 1, 4, 3 C) 3, 1, 4, 2 D) 1, 2, 3, 4

A) 4, 3, 2, 1

41) Why do histones bind tightly to DNA?

A) Histones are positively charged, and DNA is negatively charged.

32) Which of the enzymes separates the DNA strands during replication?

A) I

Which of the following statements correctly describes the effect a nonsense mutation would have on a gene? A) It introduces a premature stop codon into the mRNA. B) It changes an amino acid in the encoded protein. C)It alters the reading frame of the mRNA. D) It has no effect on the amino acid sequence of the encoded protein.

A) It introduces a premature stop codon into the mRNA.

47) In an experiment, DNA is allowed to replicate in an environment with all necessary enzymes, dATP, dCTP, dGTP, and radioactively labeled dTTP (3H thymidine) for several minutes and then switched to nonradioactive medium. It is then viewed by electron microscopy and autoradiography. The figure above represents the results.

A) There are two replication forks going in opposite directions.

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product? A) a deletion of two nucleotides B) a substitution of the first nucleotide of a GGG codon C) a substitution of the third nucleotide in an ACC codon D) a deletion of a codon

A) a deletion of two nucleotides

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following statements to be true? A) A gene from an organism can theoretically be expressed by any other organism. B) DNA was the first genetic material. C) Different organisms have different types of amino acids. D) The same codons in different organisms translate into different amino acids.

A) a gene from an organism can theoretically be expressed by any other organism.

Which of the following processes is central to the initiation of transcription? A) binding of sigma to the promoter region B) formation of a phosphodiester bond in the elongating RNA strand C) binding of DNA polymerase to the promoter region D) formation of a DNA primer

A) binding of sigma to the promoter region

49) You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent

A) leading strands and Okazaki fragments.

The mutation resulting in sickle cell anemia changes one base pair of DNA so it is an example of a _____. A) point mutation B) frameshift mutation C) silent mutation D) missense mutation

A) point mutation

26) What is the function of topoisomerase?

A) relieving strain in the DNA ahead of the replication fork

Post-translational modifications include all of the following except _____. A) removal of introns B) formation of hydrogen bonds among carbonyl and amino groups of the polypeptide backbone C) formation of covalent bonds between cysteine residues of the amino acid side chains D) addition of carbohydrates to form a glycoprotein

A) removal of introns

7) Which of the following can be determined directly from X-ray diffraction photographs of crystallized DNA?

A) the diameter of the helix

24) The leading and the lagging strands differ in that

A) the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

23) The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that

A) the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.

Which of the following processes is the first event to take place in translation in eukaryotes? A) the small subunit of the ribosome recognizes and attaches to the 5′ cap of mRNA B) the ribosome reaches a stop codon C) base pairing of activated methionine-tRNA to AUG of the messenger RNA D) binding of the larger ribosomal subunit to smaller ribosomal subunits

A) the small subunit of the ribosome recognizes and attaches to the 5′ cap of mRNA

Which of the following processes occurs in prokaryotes but not in eukaryotes? A) transcription and translation occur simultaneously B) post-transcriptional splicing C) translation in the absence of a ribosome D) gene splicing

A) transcription and translation occur simultaneously

Once a peptide has been formed between the amino acid attached to the tRNA in the P site and the amino acid associated with the tRNA in the A site, which process on the list occurs next? A) translocation B) reading of the next codon of mRNA C) initiation D) The codon-anticodon hydrogen bonds holding the tRNA in the A site are broken.

A) translocation

At which site do new aminoacyl tRNAs enter the ribosome during elongation? Select one: E-site A-site B-site P-site

A-site

At which site do new aminoacyl tRNAs enter the ribosome during elongation?

A-site This is the site at which new aminoacyl tRNAs that are complementary to the mRNA codon enter the ribosome.

At which site do new aminoacyl tRNAs enter the ribosome during elongation?

A-site. This is the site at which new aminoacyl tRNAs that are complementary to the mRNA codon enter the ribosome.

Given the DNA template shown in the associated figure, which of the following bases would you find in a complementary RNA strand and where would they be synthesized?

AAAAA Nucleus

If the DNA code for a particular amino acid is AGT, then the anticodon on the tRNA would be _____.

AGT

The nitrogenous base adenine is found in all members of which group?

ATP, RNA, and DNA

In the control of gene expression in bacteria, a regulatory gene ___________.

All of the listed responses are correct.

Death cap mushrooms produce a substance called alpha-amanitin. Alpha-amanitin efficiently blocks synthesis of mRNA, but not of tRNA or rRNA in eukaryotic organisms. How is that possible?

Alpha-amanitin efficiently interferes with the action of RNA polymerase II, but not RNA polymerase I or III.

For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins

If a mutated DNA sequence produces a protein that differs in one central amino acid from the normal protein, which of the following kinds of mutations could have occurred? Select one: An addition mutation A deletion mutation. None. An addition mutation and a deletion mutation

An addition mutation and a deletion mutation

If a mutated DNA sequence produces a protein that differs in one central amino acid from the normal protein, which of the following kinds of mutations could have occurred?

An addition mutation and a deletion mutation. If the mutations occur within the same codon, only that codon (amino acid) will be altered.

Which of the following best reflects what we know about how the flu virus moves between species?

An animal such as a pig is infected with more than one virus, genetic recombination occurs, the new virus mutates, the virus is passed to a new species such as a bird, and the virus mutates again and can now be transmitted to humans.

There are 61 codons that each specify the addition of a specific amino acid, and three stop codons for which there is no corresponding amino acid. However, there are only about 40 tRNA molecules, representing 40 anticodons. How is that possible?

An anticodon forms hydrogen bonds with the codon; it must match the first two bases of the codon, but is less specific with respect to the third base

helicase

An enzyme that unzips the double helix of DNA at the replication forks. • breaks hydrogen bonds

A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which of the following might this illustrate?

Any mutation in the sequence is selected against.

Although the expression of most genes is tightly regulated, some genes are expressed at roughly constant rates. Which of the following genes would you predict to be constitutively (constantly) expressed? a. genes involved in the degradation of tryptophan b. genes that code for regulatory proteins c. genes involved in the biosynthesis of the amino acid tryptophan d. genes involved in the degradation of arabinose, a sugar

B

An experimenter has altered the 3'end of the tRNA corresponding to the amino acid methionine in such a way as to remove the 3' bases AC. Which of the following hypotheses describes the most likely result? a. tRNA will not form a cloverleaf. b. The amino acid methionine will not become covalently bound. c. The aminoacyl-tRNA synthetase will not be formed. d. The anticodon will not bind with the mRNA codon.

B

Eukaryotes have three nuclear RNA polymerases. The primary function of RNA polymerase II is transcription of _____. a. only rRNA-coding genes b. protein-coding genes c. only tRNA-coding genes d. both rRNA- and tRNA-coding genes

B

In eukaryotes, general transcription factors _____ a. usually lead to a high level of transcription even without additional specific transcription factors b. are required for the expression of specific protein-encoding genes c. bind to other proteins or to the TATA box d. bind to sequences just after the start site of transcription e. inhibit RNA polymerase binding to the promoter and begin transcribing

B

There are sixty-one mRNA codons that specify an amino acid, but only forty-five tRNAs. This is best explained by the fact that _____. a. many codons are never used, so the tRNAs that recognize them are dispensable b. the rules for base pairing between the third base of a codon and tRNA are flexible c. some tRNAs have anticodons that recognize four or more different codons d. competitive exclusion forces some tRNAs to be destroyed by nucleases e. the DNA codes for all sixty-one tRNAs, but some are then destroyed

B

Which of the following mutations is most likely to cause a phenotypic change? a. a duplication of all or most introns b. a single nucleotide deletion in an exon coding for an active site c. a frameshift mutation one codon away from the end of the nontemplate strand d. a nucleotide substitution in an exon coding for a transmembrane domain e. a large inversion whose ends are each in the same region between genes

B

Which one of the following, if missing, would usually prevent translation from starting? a. 5' cap b. AUG codon c. poly-A tail d. exon

B

A part of an mRNA molecule with the following sequence is being read by a ribosome: 5′-CCG-ACG-3′ (mRNA). The following charged transfer RNA molecules (with their anticodons shown in the 3′ to 5′ direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form. Which of the following anticodons in the first tRNA to bind will complement this mRNA? A) 5′-GGC-3′ B) 3′-GGC-5′ C) 3′-UGC-5′ D) 5′-UGC-3′

B) 3′-GGC-5′

Use the figure to answer the question. The figure represents tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid? A) 5′-GUA-3′ B) 5′-UUC-3′ C) 5′-UGG-3′ D) 3′-GUG-5′

B) 5′-UUC-3′

4) In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?

B) DNA contains phosphorus, whereas protein does not.

56) A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?

B) DNA ligase

Which of the following statements correctly describes Archibald Garrod's hypothesis for how "inborn errors of metabolism" such as alkaptonuria occur? A) Metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies. B) Genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes. C) Enzymes are made of DNA, and affected individuals lack DNA polymerase. D) Certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors.

B) Genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.

40) Which of the following statements is true of histones?

B) Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together.

What is the function of the release factor during translation in eukaryotes? A) It releases the amino acid from its tRNA to allow the amino acid to form a peptide bond. B) It binds to the stop codon in the A site in place of a tRNA. C) It supplies a source of energy for termination of translation. D) It releases the ribosome from the ER to allow polypeptides into the cytosol.

B) It binds to the stop codon in the A site in place of a tRNA.

1) In his transformation experiments, what did Griffith observe?

B) Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.

14) In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?

B) No replication fork will be formed.

10) Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons?

B) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.

What would be the consequence of a mutation in a bacterial cell that produces a defective aminoacyl-tRNA synthetase that attaches a lysine instead of the normal phenylalanine to tRNAs with the anticodon AAA? A) None of the proteins in the cell will contain phenylalanine. B) Proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU. C) The ribosome will skip a codon every time a UUU is encountered. D) The cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons.

B) Proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.

11) What is meant by the description "antiparallel" regarding the strands that make up DNA?

B) The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

39) If a cell were unable to produce histone proteins, which of the following would be a likely effect?

B) The cell's DNA couldn't be packed into its nucleus.

36) Studies of nucleosomes have shown that histones (except H1) exist in each nucleosome as two kinds of tetramers: one of 2 H2A molecules and 2 H2B molecules, and the other as 2 H3 and 2 H4 molecules. Which of the following is supported by this data?

B) The two types of tetramers associate to form an octamer.

Which of the following statements is the most current description of a gene? A) a unit of heredity that causes formation of a phenotypic characteristic B) a DNA sequence that is expressed to form a functional product: either RNA or polypeptide C) a DNA subunit that codes for a single complete protein D) a discrete unit of hereditary information that consists of a sequence of amino acids

B) a DNA sequence that is expressed to form a functional product: either RNA or polypeptide

The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. What is the result of this type of mutation? A) a frameshift mutation B) a polypeptide missing an amino acid C) a nonsense mutation D) a base-pair substitution

B) a polypeptide missing an amino acid

Ribosomes can attach to prokaryotic messenger RNA _____. A) once post-transcriptional modification is complete B) before transcription is complete C) once replication is complete D) once the primary transcript has been released from RNA polymerase

B) before transcription is complete

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the ________. A) binding of the anticodon to small subunit of the ribosome B) binding of the anticodon to the codon and the attachment of amino acids to tRNAs C) binding of ribosomes to mRNA D) attachment of amino acids to rRNAs

B) binding of the anticodon to the codon and the attachment of amino acids to tRNAs

A single base substitution mutation is likely to have a less deleterious effect when the base change exhibits which of the following results? A)a stop codona B) codon that specifies the same amino acid as the original codon C) an amino acid substitution that alters the tertiary structure of the protein D) an amino acid substitution at the active site of an enzyme

B) codon that specifies the same amino acid as the original codon

Which of the following occurs in prokaryotes, but not eukaryotes? A) post-transcriptional splicing B) concurrent transcription and translation C) translation in the absence of a ribosome D) gene regulation

B) concurrent transcription and translation

What type of bonding is responsible for maintaining the shape of the tRNA molecule shown in the figure? A) ionic bonding between phosphates B) hydrogen bonding between base pairs C) peptide bonding between amino acids D) van der Waals interactions between hydrogen atoms

B) hydrogen bonding between base pairs

20) Polytene chromosomes of Drosophila salivary glands each consist of multiple identical DNA strands that are aligned in parallel arrays. How could these arise?

B) replication without separation

What molecule in the spliceosome lowers the activation energy so intron removal reactions can occur? A) RNA polymerase B) ribozymes C) proteins of the spliceosome D) autocatalysis by introns

B) ribozymes

The TATA box of the eukaryotic promoter is analogous to which structure of the prokaryotic promoter? A) sigma B) the -10 box C) the -35 box D) the site of initiation

B) the -10 box

How does the primary transcript in the nucleus of a prokaryotic cell compare to the functional mRNA? A) the primary transcript is larger than the mRNA B) the primary transcript is the same size as the mRNA C) the primary transcript is smaller than the mRNA D) the primary transcript and the mRNA both contain introns

B) the primary transcript is the same size as the mRNA

In humans, xeroderma pigmentosum (XP) is a disorder of the nucleotide excision repair mechanism. These individuals are unable to repair DNA damage caused by ultraviolet light. Which of the following are the most prominent types of DNA lesions in individuals suffering from xeroderma pigmentosum? A) methylation of purines B) thymine dimers C) telomere shortening D) mismatch errors

B) thymine dimers

In the accompanying image, a nucleotide is indicated by the letter _____.

B. (is indiciation a single nucleotide)

What determines which base is to be added to an RNA strand during transcription?

Base pairing between the DNA template strand and the RNA nucleotides Transcription involves the formation of an RNA strand that is complementary to the DNA template strand.

What determines which base is to be added to an RNA strand during transcription? Select one: The order of the chemical groups in the backbone of the RNA molecule The previous base Base pairing between the DNA template strand and the RNA nucleotides Base pairing between the two DNA strands

Base pairing between the DNA template strand and the RNA nucleotides Transcription involves the formation of an RNA strand that is complementary to the DNA template strand.

What would be the consequence(s) for DNA synthesis if primase were defective?

Both leading and lagging strand synthesis would be incomplete. • Primase is required to synthesize the RNA primers on both the leading and lagging strands (all DNA polymerases require a primer).

Cell differentiation always involves _____. a. the movement of cells. b. the selective loss of certain genes from the genome. c. the production of tissue-specific proteins, such as muscle actin. d. the transcription of the myoD gene. e. the cell's sensitivity to environmental cues, such as light or heat.

C

Cell differentiation always involves _____. a. the movement of cells. b. the cell's sensitivity to environmental cues, such as light or heat. c. the production of tissue-specific proteins, such as muscle actin. d. the selective loss of certain genes from the genome. e. the transcription of the myoD gene.

C

If you were to observe the activity of methylated DNA, you would expect it to _____. a. be unwinding in preparation for protein synthesis b. be very actively transcribed and translated c. have turned off or slowed down the process of transcription d. be replicating nearly continuously e. induce protein synthesis by not allowing repressors to bind to it

C

In eukaryotic cells, transcription cannot begin until _____. a. the two DNA strands have completely separated and exposed the promoter b. the DNA introns are removed from the template c. several transcription factors have bound to the promoter d. the 5' caps are removed from the mRNA e. DNA nucleases have isolated the transcription unit

C

Ribosomes can attach to prokaryotic messenger RNA _____. a. once the primary transcript has been released from RNA polymerase b. once post-transcriptional modification is complete c. before transcription is complete d. once replication is complete

C

The anticodon of a particular tRNA molecule is _____. a. complementary to the corresponding triplet in rRNA b. changeable, depending on the amino acid that attaches to the tRNA c. complementary to the corresponding mRNA codon d. the part of tRNA that bonds to a specific amino acid e. catalytic, making the tRNA a ribozyme

C

The functioning of enhancers is an example of _____. a. a post-transcriptional mechanism to regulate mRNA b. a eukaryotic equivalent of prokaryotic promoter functioning c. transcriptional control of gene expression d. post-translational control that activates certain proteins e. the stimulation of translation by initiation factors

C

Which of the following occurs in prokaryotes but not in eukaryotes? a. post-transcriptional splicing b. gene regulation c. concurrent transcription and translation d. translation in the absence of a ribosome

C

13) An Okazaki fragment has which of the following arrangements?

C) 5' RNA nucleotides, DNA nucleotides 3'

9) In an analysis of the nucleotide composition of DNA, which of the following will be found?

C) A + C = G + T

During elongation, which site in the ribosome represents the location where a codon is being read? A) E site B) P site C) A site D) small subunit

C) A site

Which of the following processes occurs when termination of translation takes place? A) The end of the mRNA molecule is reached. B) The 5′ cap is reached. C) A stop codon is reached. D) The poly-A tail is reached.

C) A stop codon is reached.

Which one of the following, if missing, would prevent transcription from starting? A) exon B) 5' cap C) AUG codon D) poly A tail

C) AUG codon

15) Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?

C) DNA polymerase III

51) What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

C) DNA polymerase can join new nucleotides only to the 3' end of a growing strand.

43) Which of the following statements describes chromatin?

C) Heterochromatin is highly condensed, whereas euchromatin is less compact.

33) Which of the enzymes covalently connects segments of DNA?

C) III

Which of the following processes occurs during transcription? A) mRNA attaches to ribosomes B) proteins are synthesized C) RNA is synthesized D) DNA is replicated

C) RNA is synthesized

16) Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?

C) gaps left at the 5' end of the lagging strand

According to the central dogma, what is the intermediate molecule involved in the flow of information in a cell that should go in the blank?DNA → ________ → Proteins A) rRNA B) tRNA C) mRNA D) mtDNA

C) mRNA

50) In his work with pneumonia-causing bacteria and mice, Griffith found that

C) some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.

The following question refers to this table of codons. Refer to the figure. Which of the triplets below is a possible anticodon for a tRNA that transports proline to a ribosome? A) 3′-CCC-5′ B)3′-UUC-5′ C)3′-GGC-5′ D)3′-CCG-5′

C)3′-GGC-5′

A nitrogenous base is indicated by the letter _______.

C. (This is a nitrogenous base)

The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence _____. Select one: CAG TCG CTG GAC CUG

CUG

Allolactose, an isomer of lactose, is formed in small amounts from lactose. An E. coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. Which of the following occurs when lactose enters the cell? a. Allolactose binds to the regulator gene. b. The repressor protein and allolactose bind to RNA polymerase. c. RNA polymerase attaches to the regulator. d. Allolactose binds to the repressor protein. e. The repressor protein attaches to the regulator.

D

Altering patterns of gene expression in prokaryotes would most likely serve an organism's survival by _____. a. organizing gene expression, so that genes are expressed in a given order b. allowing young organisms to respond differently than more mature organisms c. allowing each gene to be expressed an equal number of times d. allowing an organism to adjust to changes in environmental conditions e. allowing environmental changes to alter a prokaryote's genome

D

During elongation, which site in the ribosome represents the location where a codon is being read? a. P site b. E site c. the small ribosomal subunit d. A site

D

Once a peptide has been formed between the amino acid attached to the tRNA in the P site and the amino acid associated with the tRNA in the A site, what occurs next? a. reading of the next codon of mRNA b. The codon-anticodon hydrogen bonds holding the tRNA in the A site are broken. c. initiation d. translocation

D

Regulatory transcription factors _____. a. influence the binding of sigma factor to DNA b. open the two strands of DNA so that RNA polymerase can begin transcription c. influence the degree of unwinding of DNA at the promoter d. influence the assembly of the basal transcription complex

D

What is responsible for termination of transcription in eukaryotic protein-coding genes? a. a sigma factor b. a portion of the polymerase holoenzyme c. three nonsense mutations in sequence d. a polyadenylation signal or poly(A) e. a termination loop composed of guanine

D

Which of the following allows more than one type of protein to be produced from one gene? a. alternative forms of nucleosomes b. alternative forms of chromatin remodeling c. control of the frequency of translation initiation d. alternative forms of RNA splicing

D

Which one of the following, if missing, would usually prevent translation from starting? a. exon b. poly-A tail c. 5' cap d. AUG codon

D

Which of these is responsible for catalyzing the formation of a RNA primer?

D (Primase catalyzes the formation of an RNA primer)

Codons are three-base sequences in mRNA that specify the addition of a single amino acid to the growing protein chain during translation. How do eukaryotic codons and prokaryotic codons compare? A) Prokaryotic codons usually specify different amino acids than those of eukaryotes. B) The translation of codons is mediated by tRNAs in eukaryotes, but translation requires no intermediate molecules such as tRNAs in prokaryotes. C) Prokaryotic codons usually contain different bases than those of eukaryotes. D) Codons are a nearly universal language among all organisms.

D) Codons are a nearly universal language among all organisms.

44) In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" nitrogen (15N) and then transferred them to a medium containing 14N. Which of the results in the figure above would be expected after one round of DNA replication in the presence of 14N?

D) D

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts? A) DNA contains nitrogen, whereas protein does not. B) RNA includes ribose, whereas DNA includes deoxyribose sugars. C) DNA contains purines, whereas protein includes pyrimidines. D) DNA contains phosphorus, whereas protein does not. E) DNA contains sulfur, whereas protein does not.

D) DNA contains phosphorus, whereas protein does not

3) After mixing a heat-killed, phosphorescent strain of bacteria with a living nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observations would provide the best evidence that the ability to fluoresce is a heritable trait?

D) Descendants of the living cells are also phosphorescent.

5) Which of the following investigators was/were responsible for the following discovery? In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.

D) Erwin Chargaff

31) Which of the enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?

D) IV

What is the function of the release factor during translation in eukaryotes? A) It releases the amino acid from its tRNA to allow the amino acid to form a peptide bond. B) It supplies a source of energy for termination of translation. C) It releases the ribosome from the ER to allow polypeptides into the cytosol. D) It binds to the stop codon in the A site in place of a tRNA.

D) It binds to the stop codon in the A site in place of a tRNA.

Which of the following processes correctly describes alternative RNA splicing? A) It can allow the production of similar proteins from different RNAs. B) It is a mechanism for increasing the rate of translation. C) It increases the rate of transcription. D) It can allow the production of proteins of different sizes and functions from a single mRNA.

D) It can allow the production of proteins of different sizes and functions from a single mRNA.

38) Which of the following statements describes the eukaryotic chromosome?

D) It consists of a single linear molecule of double-stranded DNA plus proteins.

Which of the following statements describes the eukaryotic chromosome? A) It is composed of DNA alone. B) The nucleosome is its most basic functional subunit. C) The number of genes on each chromosome is different in different cell types of an organism. D) It consists of a single linear molecule of double-stranded DNA. E) Active transcription occurs on heterochromatin.

D) It consists of a single linear molecule of double-stranded DNA.

The genetic code is redundant. What is meant by this statement? A) A single codon can specify the addition of more than one amino acid. B) The genetic code is universal (the same for all organisms). C) The genetic code is different for different domains of organisms. D) More than one codon can specify the addition of the same amino acid

D) More than one codon can specify the addition of the same amino acid

Which of the following does not occur in post-transcriptional modifications occurring in eukaryotic mRNAs? A) addition of a poly (A) tail B) addition of a methyl-guanosine cap C) removal of introns D) RNA polymerase termination

D) RNA polymerase termination

46) Once the pattern found after one round of replication was observed, Meselson and Stahl could be confident of which of the following conclusions?

D) Replication is not conservative.

Use the figure to answer the question. The tRNA shown in the figure has its 3′ end projecting beyond its 5′ end. Which of the following processes will occur at this 3′ end? A) The small and large subunits of the ribosome will attach to it. B) The excess nucleotides (ACCA) will be cleaved off at the ribosome. C) The 5′ cap of the mRNA will become covalently bound. D) The amino acid binds covalently.

D) The amino acid binds covalently.

Once a peptide bond has been formed between the amino acid attached to the tRNA in the P site and the amino acid associated with the tRNA in the A site, what process occurs next? A) translocation B) reading of the next codon of mRNA C) initiation D) The codon-anticodon hydrogen bonds holding the tRNA in the A site are broken.

D) The codon-anticodon hydrogen bonds holding the tRNA in the A site are broken.

29) Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells are impaired in what way?

D) They cannot repair thymine dimers.

Which of the following statements is true about protein synthesis in prokaryotes? A) Unlike eukaryotes, prokaryotes require no initiation or elongation factors. B) Prokaryotic cells have complicated mechanisms for targeting proteins to the appropriate cellular organelles. C) Extensive RNA processing is required before prokaryotic transcripts can be translated. D) Translation can begin while transcription is still in progress.

D) Translation can begin while transcription is still in progress.

30) Which of the following would you expect of a eukaryote lacking telomerase?

D) a reduction in chromosome length in gametes

Post-translational modifications of proteins may include which of the following processes? A) addition of a poly-A tail B) addition of a 5′ cap C) removal of introns D) addition of carbohydrates to form a glycoprotein

D) addition of carbohydrates to form a glycoprotein

53) The elongation of the leading strand during DNA synthesis

D) depends on the action of DNA polymerase.

Which of the following is not one of the steps in initiation of translation? A) binding of the large ribosomal subunit to the small ribosomal subunit B) binding of tRNA carrying formyl methionine to the start codon and small ribosomal subunit C) recognition and binding of mRNA by the small ribosomal subunit D) formation of a polypeptide bond

D) formation of a polypeptide bond

Which of the following molecular structures contain codons? A) tRNA B) rRNA C) a protein D) mRNA

D) mRNA

55) E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?

D) one low-density and one intermediate-density band

Which of the following is part of a DNA molecule? A) sigma B) the holoenzyme C) initiation factors D) promoters

D) promoters

28) Which of the following help(s) to hold the DNA strands apart while they are being replicated?

D) single-strand binding proteins

37) In a linear eukaryotic chromatin sample, which of the following strands is looped into domains by scaffolding?

D) the 30-nm chromatin fiber

The enzyme that can replicate DNA is called

DNA Polymerase

What catalyzes DNA synthesis?

DNA Polymerase

Genotype is to _____ as phenotype is to _____. Select one: heredity; DNA base sequence gene regulation; translation DNA base sequence; physical traits that are products of the proteins produced transcription; amino acid sequence

DNA base sequence; physical traits that are products of the proteins produced

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

DNA in both daughter cells would be radioactive

What did Rosalind Franklin's famous photo 51 show?

DNA is a helix

Early, flawed DNA models proposed by Watson and Crick and by Linus Pauling correctly described which property of DNA?

DNA is composed of sugars, phosphate and bases

What is a difference between a DNA and RNA molecule?

DNA is usually double-stranded, whereas RNA is usually single-stranded. (With some exceptions, DNA is a double-stranded molecule and RNA is a single-stranded molecule)

Step three of lagging strand synthesis

DNA ligase closes the gap between fragments A and B.

Step two of lagging strand synthesis

DNA pol III falls off and is replaced by DNA pol I. Starting at the 5' end of primer A, DNA pol I removes each RNA nucleotide and replaces it with the corresponding DNA nucleotide. (DNA pol I adds the nucleotides to the 3' end of fragment B.) When it encounters the 5' end of fragment A, DNA pol I falls off, leaving a gap in the sugar-phosphate backbone between fragments A and B.

The enzyme that can replicate DNA is called _____.

DNA polymerase

What catalyzes DNA synthesis?

DNA polymerase

Which enzyme catalyzes the elongation of a DNA strand in the 5' --> 3' direction?

DNA polymerase III

Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments?

DNA polymerase can assemble DNA only in the 5' to 3' direction

Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments?

DNA polymerase can assemble DNA only in the 5' to 3' direction • Since DNA polymerase can assemble DNA only in the 5' to 3' direction, the new strand complementary to the 3' to 5' strand must be assembled either in short 5' to 3' segments, which are later joined together by ligase, or be assembled continuously.

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

DNA polymerase can join new nucleotides only to the 3 end of pre-existing strands, and the strands are antiparallel

A new DNA strand elongates only in the 5' to 3' direction because

DNA polymerase can only add nucleotides to the free 3' end.

The lagging strand is characterized by a series of short segments of DNA (Okazaki fragments) that will be joined together to form a finished lagging strand. The experiments that led to the discovery of Okazaki fragments gave evidence for which of the following ideas?

DNA polymerase is a directional enzyme that synthesizes leading and lagging strands during replication.

The radioactive isotope 32P labels that the T2 phage's _______.

DNA. (The T2 phage consists of a protein coat and DNA. It is the DNA that contains P)

Central dogma of molecular biology (Crick)

DNA—> RNA—> protein • DNA = hereditary material • Gene = specific stretch of DNA • DNA transcribed into mRNA since it cant leave nucleus • mRNA is translated to protein

After replication is complete, the new DNAs, called _____, are identical to each other.

Daughter DNA

If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred?

Deletion The original sequence has lost the base C.

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

Deletion of 2 nucleotides

In eukaryotes, general transcription factors _____ a. are required for the expression of specific protein-encoding genes b. bind to sequences just after the start site of transcription c. inhibit RNA polymerase binding to the promoter and begin transcribing d. usually lead to a high level of transcription even without additional specific transcription factors e. bind to other proteins or to the TATA box

E

The functioning of enhancers is an example of _____. a. a eukaryotic equivalent of prokaryotic promoter functioning b. the stimulation of translation by initiation factors c. post-translational control that activates certain proteins d. a post-transcriptional mechanism to regulate mRNA e. transcriptional control of gene expression

E

A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) in the ribosome already. Where does tRNA (#2) move after this bonding of lysine to the polypeptide?

E site

48) For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

E) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

12) Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

E) DNA in both daughter cells would be radioactive.

25) A new DNA strand elongates only in the 5' to 3' direction because

E) DNA polymerase can only add nucleotides to the free 3' end.

Which of the following is not true of enhancers?

Each gene may have several enhancers, and each enhancer may be associated with and regulate several genes.

DNA replication is said to be semiconservative. What does this mean?

Each new double helix consists of one old and one new strand

Which one of the following is true of tRNAs?

Each tRNA binds a particular amino acid. Aminoacyl-tRNA synthetase joins a specific amino acid to a tRNA, a single strand of RNA about 80 nucleotides long.

A frame shift mutation could result in

Either an insertion or deletion of base

What are their differences?

Enhancers generally are located at great distances from the promoter, whereas the araC site is located closer to the promoter.

True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated.

False There are no tRNAs complementary to the three stop codons; termination occurs when release factors recognize the stop codon in the A-site and catalyze the release of the polypeptide from the tRNA in the P-site.

True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated.

False. There are no tRNAs complementary to the three stop codons; termination occurs when release factors recognize the stop codon in the A-site and catalyze the release of the polypeptide from the tRNA in the P-site.

Who demonstrated that DNA is the genetic material of the T2 phage?

Hershey and Chase. (Hershey and Chase did a series of classic experiments demonstrating that DNA is the genetic material of the T2 phage)

Individuals who inherit mutations in p53 would be expected to have what symptoms?

Higher likelihood of developing various types of cancer In fact, people who inherit mutations in p53 do have a higher incidence of tumors, earlier in life, than those who carry only normal copies of the gene.

Individuals who inherit mutations in p53 would be expected to have what symptoms?

Higher likelihood of developing various types of cancer.

Why do histones bind tightly to DNA?

Histones are positively charged, and DNA is negatively charged.

One way that gene regulation in eukaryotic and prokaryotic cells is similar is:

In both types of cell, the primary mechanism to regulate gene expression is at the level of transcriptional regulation. Transcriptional regulation ensures the most efficient way to alter gene expression, in both prokaryotes and eukaryotes.

Why is it that bacterial ribosomes can begin translation before mRNA synthesis is completed, but eukaryotic ribosomes cannot?

In prokaryotes, transcription and translation take place in the cytoplasm. Prokaryotic cells lack a nuclear envelope.

As scientists were unraveling the mysteries associated with transcription and translation, they discovered there was not a one-to-one correspondence between nucleotide sequence of a gene and base sequence of the mRNA it codes for. They proposed the genes-in-pieces hypothesis. How can the genes-in-pieces hypothesis be explained?

Introns are noncoding segments of DNA that are present in the initial transcript, but are removed by splicing.

What is the function of the AGU on the loop of the tRNA? (image: Hairpin structure of RNA with "AGU" towards the bottom of the pin and "ACC" at the top)

It base pairs with the codon of mRNA.

There is a mutation in the repressor that results in a molecule known as a super-repressor because it represses the lac operon permanently. Which of these would characterize such a mutant?

It cannot bind to the inducer.

What is the effect of a nonsense mutation in a gene?

It introduces a premature stop codon into the mRNA.

Where does RNA polymerase begin transcribing a gene into mRNA?

It starts after a certain nucleotide sequence called a promoter. In both eukaryotes and prokaryotes, RNA polymerase binds to the gene's promoter and begins transcription at a nucleotide known as the start point, although in eukaryotes the binding of RNA polymerase to the promoter requires transcription factors.

What is the function of helicase in DNA replication?

It untwists the double helix and separates the two DNA strands.

What is the function of reverse transcriptase in retroviruses?

It uses viral RNA as a template for DNA synthesis.

Alpha-amanitin is a toxin produced by the death cap mushroom. It blocks the synthesis of mRNA. What effect would it have on health of the organism that ate death cap mushrooms?

It would cause death

Which of the following would not be true of cDNA produced using human brain tissue as the starting material?

It would contain sequences representing all the genes in the genome.

In the early 1950s, many researchers were racing to describe the structure of DNA using different approaches. Which of the following statements is true?

Jim Watson and Francis Crick built theoretical models, incorporating current knowledge about chemical bonding and X-ray data.

What would be the consequence(s) for DNA synthesis if DNA ligase were defective?

Lagging strand synthesis would be incomplete; leading strand synthesis would be largely unaffected. • Without DNA ligase activity, Okazaki fragments on the lagging strand would not be joined together; leading strand synthesis would be largely unaffected.

A primary transcript in the nucleus of a eukaryotic cell is _____ the functional mRNA, while a primary transcript in a prokaryotic cell is _____ the functional mRNA.

Larger than; the same size as

What level of transcription would you predict for a gene whose promoter is heavily methylated?

Low transcription

What level of transcription would you predict for a gene whose promoter is heavily methylated?

Low transcription Promoters in condensed DNA are inaccessible to transcriptional regulators.

For the experiment shown in Figure 19.6, what would be the conclusion if the pups from both normal-diet and low-protein mothers had similar chromatin structures and similar levels of transcription of the Hnf4a gene?

Maternal nutrition during pregnancy and lactation does not affect the gene expression of Hnf4a in their pups later in life.

For the experiment shown in Figure 19.6, what would be the conclusion if the pups from both normal-diet and low-protein mothers had similar chromatin structures and similar levels of transcription of the Hnf4a gene?

Maternal nutrition during pregnancy and lactation does not affect the gene expression of Hnf4a in their pups later in life. This experiment tested the effect of maternal nutrition on chromatin modifications in her offspring.

Who performed classic experiments that supported the semiconservative model of DNA replication?

Meselson and Stahl

What feature of the genetic code makes it possible for a single protein to be encoded by more than one mRNA sequence? Select one: The start codon also encodes methionine. There is more than one stop codon. Each codon can specify more than one amino acid. More than one codon can specify the same amino acid.

More than one codon can specify the same amino acid.

Which of the following statements explains why a larger portion of the DNA in a human cell is transcribed than would be predicted by the 1.5% of the genome that is protein-coding DNA?

Much of the non-protein-coding RNA functions to regulate the translation or degradation of mRNAs.

Which of the following is not an example of the control of gene expression after transcription?

Multiple copies of an rRNA gene are present throughout the genome.

Could you use cDNA produced from a fertilized egg to build a DNA microarray "chip" for the entire genome of the organism?

No, because cDNA is produced using the mRNA that a cell is producing, and no cell expresses all its genes at the same time.

____________ are the short sections of DNA that are synthesized on the lagging strand of the replicating DNA.

Okazaki Fragments

Which of the following processes is an example of a post-translational modification?

Phosphorylation Enzymes can phosphorylate proteins to alter their activity.

Which of these is responsible for catalyzing the formation of an RNA primer?

Primase catalyzes the formation of an RNA primer.

Which of the following statements about DNA synthesis is true?

Primers are short sequences that allow the initiation of DNA synthesis. • When a primer is added to a single strand of DNA, DNA polymerase can start adding nucleotides to synthesize a complementary strand.

What is a major difference between eukaryotic DNA replication and prokaryotic DNA replication?

Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication.

What kind of molecule is the "adapter" that couples amino acid sequences to the sequence of bases in the mRNA?

RNA tRNA transfers amino acids from RNA to the lengthening polypeptide chain.

Which of the following features is a significant difference in the function of DNA polymerases versus RNA polymerases? Select one: RNA polymerase, but not DNA polymerase, is an enzyme. RNA polymerase does not require a primer to add new nucleotides. DNA polymerase extends the growing chain in the 5' to 3' direction, whereas RNA polymerase extends growing chains from 3' to 5'. Only RNA polymerase adds nucleotide precursors (dNTPs) to a growing chain.

RNA polymerase does not require a primer to add new nucleotides.

Which of the following features is a significant difference in the function of DNA polymerases versus RNA polymerases?

RNA polymerase does not require a primer to add new nucleotides. Only DNA polymerase requires a primer.

Which of the following statements best describes the termination of transcription in prokaryotes?

RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.

In the diagram below, the gray unit represents _____.

RNA polymerase. RNA polymerase untwists a portion of the DNA double helix.

The synthesis of a new strand begins with the synthesis of a(n) _____.

RNA primer complementary to a preexisting DNA strand

The synthesis of a new strand begins with the synthesis of a(n) _______.

RNA primer complementary to a preexisting DNA strand

The synthesis of a new strand begins with the synthesis of a(n) _____.

RNA primer complementary to a preexisting DNA strand • The synthesis of a DNA strand begins with the formation of an RNA primer.

What is the function of a spliceosome?

RNA processing

What name is given to the process in which pre-mRNA is edited into mRNA? Select one: gene expression translation transcription RNA processing polypeptide formation

RNA processing

What name is given to the process in which pre-mRNA is edited into mRNA?

RNA processing RNA processing edits the RNA transcript that has been assembled along a DNA template.

In the Hershey and Chase experiment that helped confirm that DNA, not protein, was the hereditary material, what was the key finding?

Radioactively labeled phosphorus was present inside the infected bacteria. (When the bacteria had been infected with T2 phage whose DNA was tagged with radioactive phosphorus, the pellet of mainly bacterial material contained most of the radioactivity, indicating that the labeled phage DNA had entered the cells.)

DNA contains the template needed to copy itself, but it has no catalytic activity in cells. What catalyzes the formation of phosphodiester bonds between adjacent nucleotides in the DNA polymer being formed?

Selected Answer: DNA polymerase

A new DNA strand elongates only in the 5' to 3' direction because _____. DNA polymerase begins adding nucleotides at the 5' end of the template the polarity of the DNA molecule prevents addition of nucleotides at the 3' end replication must progress toward the replication fork DNA polymerase can add nucleotides only to the free 3' end

Selected Answer: DNA polymerase can add nucleotides only to the free 3' end

The lagging strand is characterized by a series of short segments of DNA (Okazaki fragments) that will be joined together to form a finished lagging strand. The experiments that led to the discovery of Okazaki fragments gave evidence for which of the following ideas? DNA polymerase is a directional enzyme that synthesizes leading and lagging strands during replication. DNA is a polymer consisting of four monomers: adenine, thymine, guanine, and cytosine. DNA is the genetic material. Bacterial replication is fundamentally different from eukaryotic replication. The key shouldn't be way longer than the distractors.

Selected Answer: DNA polymerase is a directional enzyme that synthesizes leading and lagging strands during replication

What is a major difference between eukaryotic DNA replication and prokaryotic DNA replication? Prokaryotic replication does not require a primer. Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication . DNA replication in prokaryotic cells is conservative. DNA replication in eukaryotic cells is semi-conservative. DNA polymerases of prokaryotes can add nucleotides to both 3' and 5' ends of DNA strands, while those of eukaryotes function only in the 5' → 3' direction.

Selected Answer: Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication.

Telomere shortening puts a limit on the number of times a cell can divide. Research has shown that telomerase can extend the life span of cultured human cells. How might adding telomerase affect cellular aging? Telomerase will speed up the rate of cell proliferation. Telomerase eliminates telomere shortening and retards aging. Telomerase shortens telomeres, which delays cellular aging. Telomerase would have no effect on cellular aging.

Selected Answer: Telomerase eliminates telomere shortening and retards aging.

What is meant by the description "antiparallel" regarding the strands that make up DNA? The twisting nature of DNA creates nonparallel strands. The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand. Base pairings create unequal spacing between the two DNA strands. One strand contains only purines and the other contains only pyrimidines.

Selected Answer: The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

In a healthy cell, the rate of DNA repair is equal to the rate of DNA mutation. When the rate of repair lags behind the rate of mutation, what is a possible fate of the cell? The cell can be transformed to a cancerous cell. RNA may be used instead of DNA as inheritance material. The cell will become embryonic. DNA synthesis will continue by a new mechanism.

Selected Answer: The cell can be transformed to a cancerous cell.

Put the following events of elongation in prokaryotic translation in chronological order. 1. binding of mRNA with small ribosomal subuint 2. recognition of initiation codon 3. complementary base pairing between initiation codon and anticodon of initiatior tRNA 4. base pairing of the mRNA codon following the initiator codon with its complementary tRNA Select one: a. 1,2,3,4,5 b. 2,1,4,3,5 c. 1,2,3,5,4 d. 5,4,3,2,1

The answer is: 1,2,3,5,4.

What is the difference between the leading strand and the lagging strand in DNA replication? The leading strand is synthesized in the 3' → 5' direction in a discontinuous fashion, while the lagging strand is synthesized in the 5' → 3' direction in a continuous fashion. The leading strand is synthesized continuously in the 5' → 3' direction, while the lagging strand is synthesized discontinuously in the 5' → 3' direction. The leading strand requires an RNA primer, whereas the lagging strand does not. There are different DNA polymerases involved in elongation of the leading strand and the lagging strand.

Selected Answer: The leading strand is synthesized continuously in the 5' → 3' direction, while the lagging strand is synthesized discontinuously in the 5' → 3' direction.

Which of the following statements describes a eukaryotic chromosome? a single strand of DNA a series of nucleosomes wrapped around two DNA molecules a chromosome with different numbers of genes in different cell types of an organism a single linear molecule of double-stranded DNA plus proteins

Selected Answer: a single linear molecule of double-stranded DNA plus proteins

Which of the following cells have reduced or very little active telomerase activity?

Selected Answer: most normal somatic cells

Semiconservative replication involves a template. What is the template?

Selected Answer: one strand of the DNA molecule

Telomere shortening is a problem in which types of cells?

Selected Answer: only eukaryotic cells

Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thymine and cytosine forms hydrogen bonds with guanine. This arrangement _____.

Selected Answer: permits complementary base pairing

DNA is synthesized through a process known as _____.

Selected Answer: semiconservative replication

It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following?

Selected Answer: sequence of bases

What is a telomere?

Selected Answer: the ends of linear chromosomes

The leading and the lagging strands differ in that _____. the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction the leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end the lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together the leading strand is synthesized at twice the rate of the lagging strand

Selected Answer: the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction

Which sections in mature RNA do not code for amino acids? Select one: The 5'cap does not code for amino acids. The poly(A) tail codes for the amino acid lysine. The poly(A) tail is part of mature RNA and does not code for amino acids. The 3'cap and the poly(A) tail at the 5' end are part of mature RNA and do not code for amino acids. The 5'cap and the poly(A) tail at the 3' end are part of mature RNA and do not code for amino acids

The 5'cap and the poly(A) tail at the 3' end are part of mature RNA and do not code for amino acids Experiments have shown that mRNAs with a 5' cap and a poly(A) tail last longer and produce more proteins when introduced into cells. Neither one is transcribed.

An aminoacyl-tRNA that enters the A site of the ribosome will next occupy which site?

The P site P stands for "peptidyl" and is in the middle in the ribosome.

Put the following events of transcription in chronological order. 1. sigma binds to the promoter region 2. the double helix of DNA is unwound, breaking hydrogen bonds between complementary strands. 3. sigma binds to RNA polymerase 4. sigma is released transcription begins Select one: a. 3,1,2,5,4 b. 3,2,1,4,5 c. 2,3,4,5 d. 2,3,1,4,5

The answer is: 3,1,2,5,4.

RNA polymerase needs a subunit to initiate transcription that is not needed for transcript elongation. What is the subunit? Select one: a. Rho b. Sigma c. Mg2+ d. The holoenzyme

The answer is: Sigma.

Which of the following processes is central to the initiation of transcription? Select one: a. binding of DNA polymerase to the promoter region b. formation of a DNA primer c. binding of sigma to the promoter region d. formation of a phosphodiester bond in the elongating RNA strand

The answer is: binding of sigma to the promoter region. The start codon is the same for prokaryotes and eukaryotes.

(x)Which of the following occurs in prokaryotes, but not eukaryote? Select one: a. concurrent transcription and translation b. post-transcriptional splicing c. translation in the absence of a ribosome d. gene regulation

The answer is: concurrent transcription and translation.

Which of the following is not one of the steps in initiation of translation? Select one: a. binding of the large ribosomal subunit to the small ribosomal subunit b. formation of a polypeptide bond c. binding of tRNA carrying formyl methionine to the start codong and small ribosomal subunit d. recognition and binding of mRNA by the small ribosomal subunit

The answer is: formation of a polypeptide bond.In

A primary transcript in the nucleus of a eukaryotic cell is _________the functional mRNA, while a primary transcript in a prokaryotic cell is _________ the functional mRNA. Select one: a. the same size as; larger than b. larger than; the same size as c. larger than; smaller than d. the same size as; the same size as

The answer is: larger than; the same size as.

The segments of DNA where transcription begins have a binding site for RNA polymerase. The segments are known as _________. Select one: a. sigma b. the holoenzyme c. promoters d. initiation factors

The answer is: promoters.

How does termination of translation take place? Select one: a. energy depletion causes termination b. the ribosome reaches the end of the mRNA molecule c. hairpin turns of mRNA force the ribosome off the molecule d. stop codons with no corresponding tRNAs are read

The answer is: stop codons with no corresponding tRNAs are read.

Which molecule or reaction supplies the energy for polymerization of nucleotides in the process of transcription? Select one: a. the interaction between RNA polymerase and the promoter b. ATP only c. the energy released when hydrogen bonds are broken as the DNA molecule is unwound d. the phosphate bonds in the nucleotide triphosphates that serve as substrates

The answer is: the phosphate bonds in the nucleotide triphosphates that serve as substrates.

How are RNA hairpin turns related to termination? a. Release factors bind to sites on the hairpin turn, causing release of the ENA transcript. b. the turns are formed from complementary bas pairing and cause separation the RNA transcript and RNA polymerase c. The hairpin turn prevents more nucleoside triphosphates from entering the active site of the enzymes, effectively shutting off the process of polymerization. d. A three-base repeat signals a stop sequence, and the RNA transcript is released

The answer is: the turns are formed from complementary bas pairing and cause separation the RNA transcript and RNA polymerase.

In the Morse code, a series of dots and dashes code for letters of the alphabet. How is this analogous to the genetic code? Select one: There is complementarity in the genetic code (A is complementary to T, and C is complementary to G). The machinery involved in DNA synthesis is analogous to the telegraph equipment used in sending Morse code. The bases of DNA code for the more complex amino acid sequence of the proteins in cells. The bases that make up DNA are coded by the sugar-phosphate backbone.

The bases of DNA code for the more complex amino acid sequence of the proteins in cells.

What is the difference between the core promoter and promoter-proximal regulatory elements?

The core promoter is the site for binding of proteins required for transcribing all genes, such as TATA-binding protein and RNA polymerase, but the promoter-proximal elements are unique to sets of genes that are regulated together. Promoter-proximal elements are located just upstream of the core promoter.

In comparing DNA replication with RNA transcription in the same cell, which of the following is true only of replication?

The entire template molecule is represented in the product

HIV is inactivated in the laboratory after a few minutes of sitting at room temperature, but the flu virus is still active after sitting for several hours. What are the practical consequences of these findings?

The flu virus can be transmitted more easily from person to person than HIV

How is the coordinated transcription of all the genes involved in a particular metabolic pathway brought in eukaryotes?

The genes all have the same combination of control elements in their enhancers.

Which of the following steps occurs last in the initiation phase of translation? Select one: The large ribosomal subunit joins the complex. The small subunit of the ribosome binds to the 5' cap on the mRNA A peptide bond is formed between two adjacent amino acids. An aminoacyl tRNA binds to the start codon.

The large ribosomal subunit joins the complex.

Which of the following statements best describes the promoter of a protein-coding gene?

The promoter is a nontranscribed region of a gene. The promoter is the regulatory region of a protein-coding gene at which RNA polymerase must bind to initiate transcription—it is not transcribed into the RNA.

Which of the following statements best describes the promoter of a protein-coding gene? Select one: The promoter is a site at which only RNA polymerase will bind. The promoter is a nontranscribed region of a gene. The promoter is a site found on RNA polymerase. The promoter is part of the RNA molecule itself.

The promoter is a nontranscribed region of a gene. The promoter is the regulatory region of a protein-coding gene at which RNA polymerase must bind to initiate transcription—it is not transcribed into the RNA.

Researchers found E. coli that had mutation rates 100 times higher than normal. Which of the following is the most likely cause of these results?

The proofreading mechanism of DNA polymerase was not working properly.

What is meant by translocation?

The ribosome slides one codon down the mRNA. Translocation is the process by which the ribosome slides down the mRNA so a new cycle of elongation can begin.

What is meant by translocation?

The ribosome slides one codon down the mRNA. Translocation is the process by which the ribosome slides down the mRNA so a new cycle of elongation can begin.

In addition to splicing, additional modifications at the 5' and 3' end are required to generate a mature mRNA. What is the significance of these modifications?

These modifications allow the mRNA to be recognized by the protein synthesis machinery and protect it from degradation. The 5' cap and poly-A tail added to pre-mRNA complete the transformation to mature mRNA.

In addition to splicing, additional modifications at the 5' and 3' end are required to generate a mature mRNA. What is the significance of these modifications? Select one: These modifications ensure that RNA polymerase recognizes the proper promoter sequence. These modifications allow the mRNA to be recognized by the protein synthesis machinery and protect it from degradation. These modifications ensure that the mRNA is properly spliced. hese modifications are required so that the mRNA is retained in the nucleus.

These modifications allow the mRNA to be recognized by the protein synthesis machinery and protect it from degradation. The 5' cap and poly-A tail added to pre-mRNA complete the transformation to mature mRNA.

In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" nitrogen (15N) and then transferred them to a medium containing 14N. Which of the results in Figure 16.1 would be expected after one round of DNA replication in the presence of 14N?

Tube C

If the sequence ATGCATGTCAATTGA were mutated such that a base were inserted after the first G and the third T were deleted, how many amino acids would be changed in the mutant protein? Select one: One None Three Two

Two

If the sequence ATGCATGTCAATTGA were mutated such that a base were inserted after the first G and the third T were deleted, how many amino acids would be changed in the mutant protein?

Two. The second and third codons in the new sequence are different from the original codons.

Stop codon

UAA, UAG, UGA, (dont code for amino acids; just signals to stop production)

The figure represents tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid?

UUC

A particular triplet of bases in the Coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is

UUU

phenylalanine

UUU

A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is

UUU.

Several of the different globin genes are expressed in humans, but at different times in development. What mechanism could allow for this? a. pseudogene activation b. intron activation c. differential gene regulation over time d. differential translation of mRNAs e. exon shuffling

V

Of the following, which is the most current description of a gene?

a DNA sequence that is expressed to form a functional product: either RNA or polypeptide

What is a ribozyme?

a biological catalyst made of RNA A number of examples of biological catalysts containing RNA have been discovered, including ribozymes, snRNAs, and ribosomes themselves.

What does a mutagen cause?

a change in the sequence of DNA Mutations are changes in the genetic material of the cell.

Which of the following best describes siRNA?

a double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA

Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene?

a frameshift deletion at the beginning of the gene A frameshift mutation at the beginning of a gene would affect every codon after the point where the mutation occurred. During protein synthesis, incorrect amino acids would be inserted from the point where the frameshift mutation occurred on; the resulting protein would most probably be nonfunctional. For this reason, a frameshift mutation at the beginning of a gene is generally the most severe type of mutation.

During RNA processing a(n) _____ is added to the 3' end of the RNA. Select one: modified guanine nucleotide a long string of adenine nucleotides 3' untranslated region coding segment 5' untranslated region

a long string of adenine nucleotides A poly-A tail is added to the 3' end of the RNA.

During RNA processing a(n) _____ is added to the 3' end of the RNA.

a long string of adenine nucleotides. A poly-A tail is added to the 3' end of the RNA.

Where is the start codon located? Select one: in the DNA just upstream of where transcription starts at the upstream end of the 3' untranslated region (UTR) at the very start (5' end) of the mRNA at the downstream end of the 5' untranslated region (UTR)

at the downstream end of the 5' untranslated region (UTR)

Bacterial and eukaryotic cells primarily control gene expression at the level of transcription. If instead cells exerted control of gene expression primarily at the post-translational level, what would be different? a. The ability to rapidly respond to environmental change would be reduced. b. Cells would expend significantly more energy. c. Genes would no longer be transcribed. d. Translation of mRNA into protein would not occur.

b

Ribosomes can attach to prokaryotic messenger RNA _____.

before transcription is complete

single strand binding proteins

bind to and stabilize single-stranded DNA • prevents rejoining due to hydrogen bonds

In eukaryotes, general transcription factors _____

bind to other proteins or to the TATA box

Single-strand binding proteins

bind to the single strands of DNA, preventing them from re-forming hydrogen bonds with each other and allowing synthesis to occur in both strands.

What is the event that IMMEDIATELY follows the last event of this animation?

binding of RNA polymerase to the promoter

In E. coli, tryptophan switches off the trp operon by ______.

binding to the repressor and increasing its affinity for the operator

The trp repressor blocks transcription of the trp operon when the repressor _____.

binds to tryptophan

The first class of drugs developed to treat AIDS, such as AZT, were known as reverse transcriptase inhibitors. They worked because they _____.

bonded to the viral reverse transcriptase enzyme, thus preventing the virus from making a DNA copy of its RNA genome

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the

bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.

Compare and contrast general transcription factors and sigma. What do they have in common?

both are proteins that must bind to the promoter before RNA polymerase can initiate transcription

Compare and contrast enhancers and the E. coli araC binding site. What do they have in common?

both are sites in DNA where regulatory proteins bind

Helicase

breaks the hydrogen bonds between parental DNA strands and unwinds the double helix

Identify the lagging strand during duplication of DNA starting from a double helix in the accompanying figure. d b a c

c

Which nucleic acid is translated to make a protein?

mRNA mRNA is the message that is translated to make a protein.

If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred? Select one: Deletion Both addition and deletion. None. Addition.

deletion

The elongation of the leading strand during DNA synthesis

depends on the action of DNA polymerase

primease

enzyme that builds short complementary RNA primer on each strand of DNA

DNA ligase

enzyme that chemically links DNA fragments together • catalyzes the formation of phosphodiester bonds between DNA fragments.

DNA methylation and histone acetylation are examples of _____.

epigenetic phenomena

The RNA segments joined to one another by spliceosomes are _____.

exons Exons are expressed regions.

The RNA segments joined to one another by spliceosomes are _____.

exons. Exons are expressed regions.

Which one of the following is true? A codon _____. Select one: is the basic unit of the genetic code can code for up to four different amino acids extends from one end of a tRNA molecule consists of four nucleotides

is the basic unit of the genetic code

As a result of its involvement in a chemical reaction, an enzyme.

is unchanged by the reactants or products (An enzyme is a macromolecule that acts as a catalyst, a chemical agent that speeds up a reaction without being consumed or changed by the reaction. An enzyme catalyzes a reaction by lowering the EA barrier, enabling the reactant molecules to absorb enough energy to reach the transition state. Enzymes emerge from the reaction in their original form, having neither donated nor received matter or energy from the reactants.)

On the lagging strand, DNA ligase

joins Okazaki fragments by forming phosphodiester bonds between them, thus completing DNA replication.

After allowing phages grown with bacteria in a medium that contain 32P and 35S, Hershey and Chase used a centrifuge to separate the phage ghosts from the infected cell. They then examined the infected cells and found and they contained _____, which demonstrated that ______ is the phage's genetic material.

labeled DNA; DNA

The new DNA strand that grows continuously in the 5 to 3 direction is called the

leading strand

The new DNA strand that grows continuously in the 5' to 3' direction is called the _____.

leading strand

You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent _____.

leading strands and Okazaki fragments

RNA processing converts the RNA transcript into _____. Select one: tRNA mRNA a polypeptide DNA a protein

mRNA

Which nucleic acid is translated to make a protein? Select one: DNA tRNA mRNA rRNA

mRNA

RNA processing converts the RNA transcript into _____.

mRNA The editing of the RNA transcript produces mRNA.

During RNA processing a(n) _____ is added to the 5' end of the RNA.

modified guanine nucleotide The 5' cap consists of a modified guanine nucleotide.

During RNA processing a(n) _____ is added to the 5' end of the RNA.

modified guanine nucleotide. The 5' cap consists of a modified guanine nucleotide.

Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)? Select one: One addition and two deletion mutations. One addition and one deletion mutation. One addition mutation. One deletion mutation.

one addition and one deletion

Telomere shortening is a problem in which types of cells?

only eukaryotic cells

DNA does not store the information to synthesize which of the following? Select one: DNA Proteins Organelles Messenger RNA

organelles

A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The following charged transfer RNA molecules (with their anticodons shown in the 3' to 5' direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form. tRNA Anticodon GGC CGU UGC CCG ACG CGG Amino Acid Proline Alanine Threonine Glycine Cysteine Alanine The dipeptide that will form will be

proline-threonine.

Eukaryotes have three nuclear RNA polymerases. The primary function of RNA polymerase II is transcription of _____. Select one: both rRNA- and tRNA-coding genes protein-coding genes only tRNA-coding genes only rRNA-coding genes

protein-coding genes

Which of the following did Watson and Crick already know when they were trying to determine the structure of DNA? The number of

purines is always with pyrmidines

telomere

region at either end of a eukaryotic chromosome; consisting of noncoding sequences • involved in aging as they get shorter and shorter over time

During DNA replication, an open section of DNA, in which a DNA polymerase can replicate DNA, is called the _____.

replication fork

The action of helicase creates _____

replication forks and replication bubbles

The action of helicase creates _____.

replication forks and replication bubbles

The action of helicase creates _____.

replication forks and replication bubbles • A replication fork is the transition region between paired and unpaired DNA strands.

The action of helicase creates _______.

replication forks and replication bubbles. (A replication fork is the transition region between paired and unpaired DNA strands.)

Where does translation take place? Select one: Golgi apparatus Endoplasmic Reticulum Ribosome Nucleus

ribosome

Genetic code

rules that specify relationship between sequence of nucleotides in DNA or RNA and sequence of amino acids in protein

DNA is synthesized through a process known as ________.

semiconservative replication

The reason for differences in the sets of proteins expressed in a nerve and a pancreatic cell of the same individual is that nerve and pancreatic cells contain different _____.

sets of regulatory proteins

In eukaryotic cells, transcription cannot begin until _____. Select one: the two DNA strands have completely separated and exposed the promoter several transcription factors have bound to the promoter the DNA introns are removed from the template the 5' caps are removed from the mRNA DNA nucleases have isolated the transcription unit

several transcription factors have bound to the promoter

What are primers?

short sequences that allow the initiation of DNA synthesis

In the follow-up work to the experiment shown in the figure below, the researchers used a technique that allowed them to see if two DNA sequences are in close physical proximity (association). They applied this method to examine how often an enhancer and the core promoter of the Hnf4a regulatory gene were near each other.

show a lower frequency of promoter-enhancer association.

Which of the following help(s) to hold the DNA strands apart while they are being replicated?

single-strand DNA binding proteins

What helps to hold the DNA strands apart while they are being replicated?

single-strand binding proteins

Spliceosomes are composed of _____. Select one: he RNA transcript and protein polymerases and ligases introns and exons small RNAs and proteins

small RNAs and proteins

In Griffith work with pneumonia-causing bacteria and mice, he found that

some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic

What is this an image of? The figure shows a cylinder, which is formed by spirally stranded fiber. The cylinder is hollow inside. (Thick purple spiral: Part D)

supercoils

DNA polymerase III

synthesizes new DNA only in the 5' to 3' direction • starts DNA synthesis at the 3' end of a primer. • "start here" signal for DNA replication • has ability to act as exonuclease to proofread and correct complementary base pairing mistakes

DNA Polymerase III

synthesizes the new strands, but requires an existing 3 hydroxyl to add nucleotides

The RNA that has an amino acid attached to it, and that binds to the codon on the mRNA, is called a

tRNA

Sort each description by the type of RNA it describes.

tRNA: contains an anticodon, has amino acids covalently attached to it mRNA: contains exons, specifies the amino acid sequence for a protein rRNA: is a component of ribosomes, is the most abundant form of RNA

An old DNA strand is used as a _____ for the assembly of a new DNA strand.

template

An old DNA strand is used as a _______ for the assembly of a new DNA strand.

template

___________ of translation happens when the ribosome hits a stop codon on the mRNA.

termination

If a particular operon encodes enzymes for making an amino acid and is regulated like the trp operon, then _______.

the amino acid acts as a corepressor

What ensures that the correct amino acid is added during translation? Select one: the poly-A tail of a properly modified mRNA the twisting number of a properly supercoiled DNA the anticodon of a properly formed aminoacyl tRNA the methyl-guanosine cap of a properly modified mRNA

the anticodon of a properly formed aminoacyl tRNA

What determines the nucleotide sequence of the newly synthesized strand during DNA replication?

the nucleotide sequence of the template strand

Which of the following is an example of post-transcriptional control of gene expression?

the removal of introns and alternative splicing of exons

There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that

the rules for base pairing between the third base of a codon and tRNA are flexible.

In eukaryotes, the size of the primary transcript is generally ________ the gene in the template DNA strand.

the same length as The primary transcript is an exact RNA copy of the DNA coding sequence.

What name is given to the process in which a strand of DNA is used as a template for the manufacture of a strand of pre-mRNA? Select one: RNA processing transcription polypeptide formation translation gene expression

transcription

What name is given to the process in which a strand of DNA is used as a template for the manufacture of a strand of pre-mRNA?

transcription Transcription is the process by which a DNA template is used for the manufacture of several different types of RNA.

Beginning within the nucleus, the first step leading to the synthesis of a polypeptide is _____. linking of nucleotides to form a polypeptide translation of an RNA nucleotide sequence into a sequence of amino acids translation of a DNA nucleotide sequence into a sequence of amino acids removal of introns from RNA and the stitching together of exons transferring of information from DNA to messenger RNA

transferring of information from DNA to messenger RNA

What name is given to the process in which a the information encoded in a strand of mRNA is used to construct a protein? Select one: transcription RNA processing polypeptide formation translation . gene expression

translation

MicroRNAs control gene expression at the level of _______.

translation Either the mRNAs are cut and degraded, or they are blocked from interacting with ribosomes.

What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?

translation Translation is the process by which information encoded in RNA is used to manufacture a polypeptide.