Mastering Biology Exam 3
A promoter is _____. A. a sequence in DNA that binds RNA polymerase near the site for transcription B. one or more eukaryotic proteins that bind to DNA near the start of a gene C. a protein that associates with bacterial RNA polymerase to allow it to bind to DNA D. a sequence in RNA that promotes the release of RNA polymerase from DNA
A
An old DNA strand is used as a _____ for the assembly of a new DNA strand. A. template B. primer C. source of nucleotides D. complement E. model
A
DNA replication is highly accurate. It results in about one mistake per billion nucleotides. For the human genome, how often would errors occur? A. on average, 6 times each time the entire genome of a cell is replicated B. on average, once every 6 cell divisions C. on average, once a lifetime in 10% of the population D. on average, once or twice in the lifetime of an individual
A
Death cap mushrooms produce a substance called -amanitin. Alpha-amanitin efficiently blocks synthesis of mRNA, but not of tRNA or rRNA in eukaryotic organisms. How is that possible? A. Alpha-amanitin efficiently interferes with the action of RNA polymerase II, but not RNA polymerase I or III. B. Alpha-amanitin efficiently interferes with the action of RNA polymerase I, but not RNA polymerase II or III. C. Alpha-amanitin efficiently blocks the action of one or more basic transcription factors. D. Alpha-amanitin efficiently interferes with RNA polymerase III, but not RNA polymerase I and II.
A
During transcription, in what direction is (1) RNA synthesized and (2) the DNA template "read"? A. (1) 5'→3'; (2) 3'→5' B. (1) 3'→;5'; (2) 3'→5' C. (1) 5'→;3' (2) 5'→;3' D. (1) 3'→5'; (2) 5'→3'
A
If DNA repair mechanisms fail, which of the following is not a direct result? A. DNA polymerase is slower at replicating DNA. B. a mutation C. cancer D. a defective enzyme
A
________ are the short sections of DNA that are synthesized on the lagging strand of the replicating DNA.
Okazaki fragments
The now-uncharged tRNA that was in the _____ enters the ____.
P site; E site
The new DNA strand that grows continuously in the 5' to 3' direction is called the _____.
leading strand
During prophase, the microtubules of the mitotic spindle ___________.
lengthen
During anaphase, the nonkinetochore microtubules __________ and move past each other, and the kinetochore microtubules ___________.
lengthen; shorten
The ribosome moves down the _____.
mRNA
The __________ is a cell structure consisting of microtubulues, which forms during early mitosis and plays a role in cell division.
mitotic spindle
During telophase, the nonkinetochore microtubules __________.
disassemble
During DNA replication, an open section of DNA, in which a DNA polymerase can replicate DNA, is called a ________.
replication fork
DNA replication produces two identical DNA molecules, called __________, which separate during mitosis.
sister chromatids
A peptide bond forms between the polypeptide held by the _____ in the ______ and the amino acid held by the ______ in the ______.
tRNA; P site; tRNA; A site
The enzyme that removes twists in DNA ahead of the replication fork is _____.
topoisomerase
The table below shows four possible mRNA products of this gene. Use the labels to explain what mutation(s) may have resulted in each mRNA. Drag the correct label to each location in the table. Labels may be used once, more than once, or not at all.
1. mutation in a splicing signal sequence in intron 2 2. mutation in the gene's promoter sequence 3. mutations in splicing signal sequences in both intron 1 and intron 2 4. no mutation in any splicing signal sequence
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. A. thymine ... cytosine B. cytosine ... thymine C. cytosine ... uracil D. uracil ... cytosine E. guanine ... adenine
A
In human and many other eukaryotic species' cells, the nuclear membrane has to disappear in order for what to take place? A. attachment of mitotic spindle to kinetochores B. splitting of the centrosomes C. cytokinesis D. disassembly of the nucleolus
A
In the experiment shown in the figure, incorporation of a radioactive nucleotide was used to follow excision repair after exposure of cells to UV light. Which type of nucleotide is appropriate here? A. one containing deoxyribose and thymine B. one containing deoxyribose and uracil C. one containing thymine and a single phosphate group D. one containing ribose and thymine
A
Myosin is a motor protein involved in animal cell cytokinesis. It binds to ATP or ADP, causing the myosin to move with respect to actin. What is the effect of the interaction between myosin and actin? A. The cleavage furrow deepens. B. Vesicles containing plasma membrane constituents are transported to the metaphase plate, where cytokinesis takes place. C. Excess cytoplasm is removed. D. It triggers the reformation of the daughter nuclei.
A
Once a cell completes mitosis, molecular division triggers must be turned off. What happens to MPF during mitosis? A. Cyclin is degraded; the concentration of cyclin-dependent kinase remains unchanged, but without cyclin, MPF is not formed. B. It is completely degraded. C. Cyclin-dependent kinase is degraded; cyclin concentration remains constant, but without cyclin-dependent kinase, MPF is not formed. D. It is exported from the cell.
A
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. Put the following events of transcription in chronological order. A. 3, 1, 2, 5, 4 B. 2, 3, 4, 5 C. 3, 2, 1, 4, 5 D. 2, 3, 1, 4, 5
A
Telomerase is needed to _____. A. prevent the loss of DNA from chromosome ends B. create repetitive DNA sequences that allow the assembly of the kinetochore C. allow DNA replication at the ends of chromosomes to occur in the 3' - 5' direction D. open the two strands of DNA in front of the replication fork
A
The M-phase checkpoint is designed to make sure all chromosomes are attached to the mitotic spindle. If this fails to happen, in which stage of mitosis would the cells be most likely to arrest? A. metaphase B. prophase C. prometaphase D. telophase
A
The action of helicase creates _____. A. replication forks and replication bubbles B. primers and replication bubbles C. DNA fragments and replication bubbles D. primers and DNA fragments E. DNA fragments and replication forks
A
The first step in the replication of DNA is catalyzed by _____. A. helicase B. ligase C. DNA polymerase D. single-strand binding protein E. primase
A
What happens when MPF (mitosis-promoting factor) is introduced into immature frog oocytes that are arrested in G2? A. The cells enter mitosis. B. Cell differentiation is triggered. C. Fertilization occurs. D. Nothing happens.
A
What is a telomere? A. the ends of linear chromosomes B. the mechanism that holds two sister chromatids together C. the site of origin of DNA replication D. the reorganization of the cell nucleus that takes place during telophase
A
What is the function of primase? A. synthesis of a short section of RNA, complementary to single-stranded DNA B. removing primers and synthesizing a short section of DNA to replace them C. closing the gap at the 39 end of DNA after excision repair D. synthesis of the short section of double-stranded DNA required by DNA polymerase
A
What molecule is responsible for the catalytic activity in the spliceosomes that are involved in removal of introns? A. ribozymes B. autocatalysis by introns C. RNA polymerase D. proteins of the spliceosome
A
Which answer correctly identifies a cell-cycle checkpoint with a criterion for passing it? A. G2 checkpoint: Chromosomes have replicated successfully. B. Metaphase checkpoint: DNA is undamaged. C. G1 checkpoint: Chromosomes have replicated successfully. D. S checkpoint: DNA is undamaged
A
Which of the following cells do not have active telomerase activity? A. most normal somatic cells B. most cancer cells C. most normal germ cells
A
Which of the following statements about DNA synthesis is true? A. Primers are short sequences that allow the initiation of DNA synthesis. B. As DNA polymerase moves along the template strand, each new nucleotide provides a 5' hydroxyl group for the next reaction to occur. C. DNA polymerase adds dNTP monomers in the 3' to 5' direction. D. Nucleotides are added in a random fashion to single-stranded DNA.
A
Which part of a deoxynucleoside triphosphate (dNTP) molecule provides the energy for DNA synthesis? A. Phosphate groups B. Sugar C. Free 3' hydroxyl (-OH) group D. Base
A
Why does telomerase need to have a built-in template for DNA synthesis? A. Telomerase is involved in adding DNA to the end of the lagging strand. B. Telomerase is involved in adding DNA to the end of the leading strand. C. All of lagging strand synthesis requires genetic information that is not present in the parent DNA molecule. D. All of leading strand synthesis requires genetic information that is not present in the parent DNA molecule.
A
After replication is complete, the new DNAs, called _______, are identical to each other.
daughter DNA
The tRNA holding the polypeptide chain moves from the _____ to the _____.
A site; P site
After transcription begins, several steps must be completed before the fully processed mRNA is ready to be used as a template for protein synthesis on the ribosomes. Which three statements correctly describe the processing that takes place before a mature mRNA exits the nucleus? A. A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA. B. Coding sequences called exons are spliced out by ribosomes. C. A translation stop codon is added at the 3' end of the pre-mRNA. D. Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes. E. A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA.
A, D, E
Drag the arrows onto the diagram below to indicate the direction that DNA polymerase III moves along the parental (template) DNA strands at each of the two replication forks. Arrows can be used once, more than once, or not at all.
A. --> B. --> C. <-- D. <--
The DNA double helix is composed of two strands of DNA; each strand is a polymer of DNA nucleotides. Each nucleotide consists of a sugar, a phosphate group, and one of four nitrogenous bases. The structure and orientation of the two strands are important to understanding DNA replication. Drag the labels to their appropriate locations on the diagram below. Pink labels can be used more than once.
A. 5' end B. hydrogen bond C. 3' end D. deoxyribose sugar E. nitrogenous base F. phosphate group G. 3' end H. 5' end
If a cell has accumulated DNA damage, it is unlikely to ________. A. activate DNA repair mechanisms. B. pass the G2 checkpoint. C. enter G1 from mitosis. D. synthesize cyclin-dependent kinases.
B
After DNA replication is completed, _____. A. there are four double helices B. each new DNA double helix consists of one old DNA strand and one new DNA strand C. one DNA double helix consists of two old strands and one DNA double helix consists of two new strands D. each of the four DNA strands consists of some old strand parts and some new strand parts E. each new DNA double helix consists of two new strands
B
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. 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
B
According to the data in Figure 11.4 in the textbook, the first labeled mitotic cells appear about 4 hours after the labeling period ends. From these data, researchers concluded that G2 lasted about 4 hours. Why? A. Cyclins were labeled, so their concentration had to build up for 4 hours. B. Labeled cells are in S phase, so 4 hours passed between the end of S phase and the onset of M phase. C. The lengths of the total cell cycle and the G1, S, and M phases were known, so the length of G2 could be found by subtraction. D. It confirmed other data indicating that G2 lasts about 4 hours in cultured cells of this type.
B
In DNA replication in bacteria, the enzyme DNA polymerase III (abbreviated DNA pol III) adds nucleotides to a template strand of DNA. But DNA pol III cannot start a new strand from scratch. Instead, a primer must pair with the template strand, and DNA pol III then adds nucleotides to the primer, complementary to the template strand. Each of the four images below shows a strand of template DNA (dark blue) with an RNA primer (red) to which DNA pol III will add nucleotides. In which image will adenine (A) be the next nucleotide to be added to the primer?
B
Nerve cells lose their ability to undergo mitosis. Instead, they are permanently stuck in ________. A. S of interphase. B. G0. C. meiosis. D. G2.
B
The micrograph shows a DNA-mRNA hybrid. If the noncoding regions of the gene did not exist, what would the micrograph look like? A. Some, but not all, of the loops would be missing. B. All of the loops would be missing. C. There would be the same number of loops, but they would be smaller. D. There would be additional loops.
B
The normal function of the Rb protein is to bind to E2F, inactivating it. What are the consequences of defects in Rb? A. It no longer responds to phosphorylation - it cannot be regulated. B. It does not bind to E2F properly, so E2F continuously stimulates the production of molecules needed in S phase. C. Rb acts as a tumor suppressor, similar in function to p53. D. It binds more tightly to E2F, so E2F cannot stimulate the production of molecules needed in S phase. The cell cannot progress through the cell cycle.
B
The wobble hypothesis explains ______. A. the redundancy of the genetic code B. the ability of some tRNAs to read more than one codon C. the fact that there are three nucleotides per codon D. the imprecise fit between aminoacyl tRNA synthetases and their substrates
B
What two types of defects does a cancerous cell possess? A. Cancerous cells possess defects that make proteins required for cell growth inactive and tumor suppressor genes active. B. Cancerous cells possess defects that make proteins required for cell growth active and tumor suppressor genes inactive. C. Cancerous cells lack the ability to carry out cellular respiration and photosynthesis. D. Cancerous cells are prevented from dividing and have inhibited growth patterns.
B
What would be the consequence(s) for DNA synthesis if primase were defective? A. Both leading and lagging strand synthesis would be unaffected. B. Both leading and lagging strand synthesis would be incomplete. C. Lagging strand synthesis would be incomplete; leading strand synthesis would be unaffected. D. Leading strand synthesis would be incomplete; lagging strand synthesis would be unaffected.
B
Which of the following is not an effect of mitosis-promoting factor (MPF) involved in moving a cell into M phase? A. phosphorylation of an enzyme that breaks down the cyclin molecule B. degradation of cyclin-dependent kinase C. phosphorylation of microtubule associated proteins, triggering the formation of the mitotic spindle D. phosphorylation of lamins, initiating breakdown of the nuclear membrane
B
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 formed on the lagging strand of DNA. C. They are usually 50 to 500 bases long. D. They are synthesized in the 3' to 5' direction.
B
Who performed the classic experiments that proved DNA was copied by semiconservative replication? A. Hershey and Chase B. Meselson and Stahl C. Franklin and Wilkins D. Watson and Crick
B
Why are ribonucleoside triphosphates the monomers required for RNA synthesis rather than ribonucleoside monophosphates? A. Only ribonucleoside triphosphates contain the sugar ribose. B. Ribonucleoside triphosphates have high potential energy, making the polymerization reaction exergonic. C. Ribonucleoside triphosphates have low potential energy, making the polymerization reaction endergonic. D.Ribonucleoside monophosphates cannot form complementary base pairs with the DNA template.
B
Why do gap phases exist in the cell cycle? A. They allow chromosomes to condense prior to mitosis. B. They allow cells to replicate organelles and manufacture additional cytoplasm. C. They allow the nuclear envelope to re-form after mitosis. D. They allow chromosome replication to occur.
B
Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments? A. only short DNA sequences can extend off the RNA primers B. DNA polymerase can assemble DNA only in the 5' to 3' direction C. DNA polymerase can assemble DNA only in the 3' to 5' direction D. it is more efficient than assembling complete new strands E. the replication forks block the formation of longer strands
B
Bodnar et al. (1998) used telomerase to extend the life span of normal human cells. Telomere shortening puts a limit on the number of times a cell can divide. How might adding telomerase affect cellular aging? A. Telomerase would have no effect on cellular aging. B. Telomerase will speed up the rate of cell proliferation. C. Telomerase ensures that the ends of the chromosomes are accurately replicated and eliminates telomere shortening. D. Telomerase shortens telomeres and thus delays cellular aging.
C
DNA replication is highly accurate. It results in about one mistake per billion nucleotides. For the human genome, how often would errors occur? A. on average, once a lifetime in 10% of the population B. on average, once every 6 cell divisions C. on average, 6 times each time the entire genome of a cell is replicated D. on average, once or twice in the lifetime of an individual
C
Following the attachment of spindle microtubules to kinetochores, chromosomes are moved around by ________. A. histones. B. motor activity taking place in the centrosomes. C. elongation and shortening of microtubules. D. myosin motor proteins
C
How does the bacterial ribosome recognize where to start translation? A. The small ribosomal subunit binds to the 5' cap of the mRNA. B. The small ribosomal subunit binds to the 3' poly(A) tail of the mRNA. C. The small ribosomal subunit binds to a sequence in the mRNA just upstream of the start codon. D. The small ribosomal subunit binds to the start codon.
C
How does the simple primary and secondary structure of DNA hold the information needed to code for the many features of multicellular organisms? A. The amino acids that make up the DNA molecule contain the information needed to make cellular proteins. B. The covalent bonding among backbone constituents contains the information that is passed from generation to generation. C. The base sequence of DNA carries all the information needed to code for proteins. D. The hydrogen bonding among backbone constituents carries coded information.
C
How many copies of DNA polymerase III are in the replisome? A. none B. one C. two D. three
C
In eukaryotes, when mature mRNA is hybridized to complementary DNA, ______. A. exons loop out as single-stranded regions of RNA B. introns loop out as single-stranded regions of RNA C. introns loop out as single-stranded regions of DNA D. exons loop out as single-stranded regions of DNA
C
Metaphase occurs prior to the splitting of centromeres. It is characterized by ________. A. cytokinesis. B. disassembly of the nuclear envelope. C. aligning of chromosomes on the equator. D. duplication of centrioles.
C
Once a cell completes mitosis, molecular division triggers must be turned off. What happens to MPF during mitosis? A. It is completely degraded. B. The cyclin-dependent kinases take on a function unrelated to mitosis. C. Cyclin is degraded; the concentration of cyclin-dependent kinase remains unchanged, but without cyclin, MPF is not formed. D. Cyclin-dependent kinase is degraded; cyclin concentration remains constant, but without cyclin-dependent kinase, MPF is not formed.
C
Which of the following is not a property of DNA polymerase? A. It can proofread because it has an exonuclease activity. B. It requires a primer to work. C. It catalyzes the addition of dNTPs only in the 5′→3′ direction. D. It is associated with a sliding clamp only on the leading strand.
D
Once researchers understood that chromosomes are moved by the spindle microtubules, the next question they wanted to answer is how the microtubules function to bring about this process. They used fluorescent labels to make the chromosomes and the microtubular structures fluoresce. When anaphase began (centromeres split), they photobleached a section of microtubules. As chromosomes moved toward the poles of the daughter cells, the photobleached sections of the microtubules remained stationary. This result suggests that ________. A. the microtubules elongate and shorten at the centrosome end. B. the microtubules are of constant length; centrosomes move farther apart to separate chromosomes. C. the microtubules elongate and shorten at their kinetochore end. D. the microtubules overlap, and slide with respect to each other, effectively shortening the microtubules without depolymerizing the actual fiber.
C
Recent studies have shown that xeroderma pigmentosum (an error in the nucleotide excision repair process) can result from mutations in one of seven genes. What can you infer from this finding? A. These mutations have resulted from translocation of gene segments. B. These seven genes are the most easily damaged by ultraviolet light. C. There are several enzymes involved in the nucleotide excision repair process. D. There are seven genes that produce the same protein.
C
Researchers found E. coli that had mutation rates 100 times higher than normal. What is a possible explanation for these results? A. There were one or more mismatches in the RNA primer. B. The DNA polymerase was unable to add bases to the 3 end of the growing nucleic acid chain. C. The proofreading mechanism of DNA polymerase was not working properly. D. The single-stranded binding proteins were malfunctioning.
C
The M-phase checkpoint is designed to make sure all chromosomes are attached to the mitotic spindle. If this fails to happen, in which stage of mitosis would the cells be most likely to arrest? A. telophase B. prometaphase C. metaphase D. prophase
C
The primers used for DNA synthesis are _____. A. short DNA sequences B. short amino acid sequences (peptides) C. short RNA sequences D. proteins that bind to single-stranded DNA
C
The synthesis of a new strand begins with the synthesis of a(n) _____. A. Okazaki fragment B. short pieces of DNA C. RNA primer complementary to a preexisting DNA strand D. single-strand binding protein E. poly(A) tail
C
What chemical force(s) stabilize(s) DNA's secondary structure? A. hydrogen bonds only B. phosphodiester bonds C. hydrogen bonds and hydrophobic interactions D. ionic bonds
C
What is the difference between the leading strand and the lagging strand in DNA replication? A. The leading strand requires an RNA primer, whereas the lagging strand does not. B. 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. C. The leading strand is synthesized continuously in the 5′→3′ direction, while the lagging strand is synthesized discontinuously in the 5′→3′ direction. D. There are different DNA polymerases involved in elongation of the leading strand and the lagging strand.
C
What is the final result of the mitosis of a 1n somatic cell? A. genetically identical 2n somatic cells B. genetically identical 2n gamete cells C. genetically identical 1n somatic cells D. genetically different 2n somatic cells
C
What provides the energy for the polymerization reactions in DNA synthesis? A. breaking the hydrogen bonds between complementary DNA strands B. the deoxyribonucleotide triphosphate substrates C. DNA polymerase D. ATP
C
Which of the following agents are unlikely to cause mutations in DNA? A. aflatoxins that are found in moldy grains B. free radicals that are formed as by-products of aerobic respiration C. radiation from an incandescent lightbulb D. ultraviolet radiation from sunlight
C
Which statement is correct concerning DNA synthesis catalyzed by DNA polymerase? A. The new DNA strand is synthesized in the 3'→5' direction; the template strand is read in the 5'→3' direction. B. The new DNA strand is synthesized in the 5'→3' direction; the template strand is read in the 5'→3' direction. C. The new DNA strand is synthesized in the 5'→3' direction; the template strand is read in the 3'→5' direction. D. The new DNA strand is synthesized in the 3'→5' direction; the template strand is read in the 3'→5' direction.
C
Which statement is correct concerning the relationship between chromosomes and genes, chromatin, or sister chromatids? A. Each unreplicated chromosome consists of two sister chromatids. B. Chromatin is a length of DNA in a chromosome that codes for a protein or RNA. C. Each replicated chromosome consists of two sister chromatids. D. Genes are the DNA - protein material that make up entire chromosomes.
C
During transcription in eukaryotes, a type of RNA polymerase called RNA polymerase II moves along the template strand of the DNA in the 3'→5' direction. However, for any given gene, either strand of the double-stranded DNA may function as the template strand. For any given gene, what ultimately determines which DNA strand serves as the template strand? A. which of the two strands of DNA carries the RNA primer B. the location of specific proteins (transcription factors) that bind to the DNA C. the location along the chromosome where the double-stranded DNA unwinds D. the base sequence of the gene's promoter
D
Following the attachment of spindle microtubules to kinetochores, chromosomes are moved around by _____. A. motor activity taking place in the centrosomes B. actin filaments C. myosin motor proteins D. elongation and shortening of microtubules
D
Imagine that the DNA strand shown below serves as the template for DNA synthesis. 5' CATGCATAGA 3' Assuming no errors in DNA synthesis, what would the new DNA look like? A. 5' GTACGTATCT 3' B. 5' TCTATCCATG 3' C. 5' UCUAUGCAUG 3' D. 5' TCTATGCATG 3'
D
Progression through the cell cycle is regulated by oscillations in the concentration of which type of molecule? A. cyclin-dependent kinases B. receptor tyrosine kinases C. p53, Rb, and other tumor suppresssors D. cyclins
D
Proteins that degrade cyclin are activated by events that MPF initiates. Why is this important for cell-cycle regulation? A. It results in the increase in cyclin concentration during interphase. B. It results in a Cdk concentration that is more or less constant throughout the cell cycle. C. It causes MPF activity to increase during M phase. D. It sets up an oscillation in cyclin concentration.
D
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. A. 3, 2, 1, 5, 4 B. 1, 2, 3, 4, 4 C. 1, 2, 3, 4, 5 D. 2, 1, 3, 5, 4
D
Regulatory proteins that serve to prevent a cell from entering the S phase under conditions of DNA damage are also known as ________. A. antibodies. B. cyclins. C. cyclin-dependent kinases. D. tumor suppressors.
D
Researchers pulsed rapidly dividing cultured cells for 30 minutes with radioactive thymidine. The cells were then exposed to a solution containing non-radiolabeled thymidine. Cells were analyzed at 2-hour intervals. At the 2-hour time point, no cells appeared to be dividing. Only after 4 hours did some labeled cells appear to be in M phase. This result can be explained in the following way: A. Radiolabeled compounds are somewhat cytotoxic, and so cell division was initially inhibited. B. Synthesis (S) phase is lengthy-about 12 hours in most cell types-and the radioactive thymidine was not present long enough for most cells to be labeled. C. The cells were arrested in a nondividing state because of the treatment and could not enter M phase until several hours after the label was removed. D. There seems to be a gap or a lag in the cell cycle, between the synthesis of DNA and cell division.
D
The TATA box of the eukaryotic promoter is analogous to which structure of the prokaryotic promoter? A. the -35 box B. the site of initiation C. sigma D. the -10 box
D
The experiment that removed proteins, RNA, or DNA from Streptococcus extracts purported to show that DNA is the hereditary material. Why did it fail to convince many skeptics? A. The trait that was studied - virulence - is not genetic. B. Genes had already been shown to be made of protein. C. It had no control treatments, so it was poorly designed. D. Critics argued that the chemical treatments had not removed all of the protein present.
D
The segments of DNA where transcription begins have a binding site for RNA polymerase. These segments are known as ________. A. sigma. B. initiation factors. C. the holoenzyme. D. promoters.
D
Toposiomerase works to _____. A. open up the two strands of DNA at the replication fork B. incorporate new DNA building blocks in the growing DNA strand C. recognize origins of replication and open a replication bubble at these sites D. prevent twisting of DNA in front of the replication fork
D
What catalyzes DNA synthesis? A. Primer B. dNTPs C. Replication fork D. DNA polymerase
D
What evidence suggests that during anaphase, spindle fibers shorten at the kinetochore and not at the base of the mitotic spindle? A. When fluorescing microtubules are bleached in the middle, the bleached segment moves toward the base of the mitotic spindle as the fibers shorten near the microtubule organizing center. B. Motor proteins are located at the kinetochore and at the base of the mitotic spindle. C. Motor proteins are located at the kinetochore. D. When fluorescing microtubules are bleached in the middle, the bleached segment stays stationary as the fibers shorten near the kinetochore.
D
What is the function of the group of amino acids on the RNA polymerase, called the rudder? A. It helps sigma bind to the RNA polymerase molecule. B. It provides the energy required for formation of phosphodiester bonds in the elongation RNA molecule. C. It helps unwind and open the DNA molecule. D. It moves template and non-template strands of DNA through channels inside the enzyme.
D
What is the function of topoisomerase? A. holding DNA polymerase steady as it moves down the leading or lagging strand B. opening the DNA helix at the replication fork C. stabilizing single strands of DNA, once the replication fork is open D. preventing kinks in DNA as the replication fork opens and unwinds
D
Which answer correctly associates a distinctive event in mitosis with the mitotic subphase when it occurs? A. Prophase: Chromosomes are replicated. B. Prometaphase: Chromosomes complete their migration to the middle of the cell. C. Telophase: Chromosomes condense. D. Anaphase: Sister chromatids separate.
D
Which of the following enzymes creates a primer for DNA polymerase? A. Helicase B. Ligase C. Topoisomerase D. Primase
D
Which of the following enzymes is important for relieving the tension in a helix as it unwinds during DNA synthesis? A. Ligase B. Single-stranded binding proteins C. Helicase D. Topoisomerase
D
Which of the following statements about transcription is correct? A. The bacterial promoter lies just downstream of the start site of transcription. B. The bacterial RNA holoenzyme is used during the elongation phase of transcription. C. Sigma factor is needed to recognize the transcriptional termination signal. D. During elongation, the RNA strand is extended in the 5' to 3' direction.
D
Which of the following would be least likely to cause DNA damage in an individual suffering from xeroderma pigmentosum? A. natural lighting B. low-level ultraviolet lights C. reflected sunlight D. incandescent lightbulbs
D
The enzyme that can replicate DNA is called _____.
DNA 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 always pairs with a(n) _____ of the complementary strand. A. cytosine ... thymine B. guanine ... adenine C. cytosine ... uracil D. uracil ... cytosine E. thymine ... cytosine
E
An uncharged tRNA leaves the ____.
E site
_________ microtubules from each pole overlap in the region of the metaphase plate.
Nonkinetochore
_____________ microtubules do not attach to the chromosomes.
Nonkinetochore
____________ microtubules position the sister chromatids along the metaphase plate.
Kinetochore
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.
True
Suppose that a portion of double-stranded DNA in the middle of a large gene is being transcribed by an RNA polymerase. As the polymerase moves through the sequence of six bases shown in the diagram below, what is the corresponding sequence of bases in the RNA that is produced? Diagram of DNA showing a coding strand and a template strand. Coding strand from 3' to 5' reads C C G A G T. Template strand from 5' to 3' reads G G C T C A. Enter the sequence of bases as capital letters with no spaces and no punctuation. Begin with the first base added to the growing RNA strand, and end with the last base added.
UGAGCC
The diagram below shows a bacterial replication fork and its principal proteins. Drag the labels to their appropriate locations in the diagram to describe the name or function of each structure. Use pink labels for the pink targets and blue labels for the blue targets.
a. Breaks hydrogen bonds, unwinding DNA double helix. b. Synthesizes RNA primers on leading and lagging strands. c. Replaces RNA primers with DNA nucleotides. d. Catalyzes phosphodiester bond formation, joining DNA fragments. e. Lagging strand f. Leading strand g. Relaxes supercoiled DNA. h. Coats single-stranded DNA. i. Synthesizes DNA 5' to 3' on leading and lagging strands.
A new _____ enters the A site.
aminoacyl tRNA
A new _____ enters the _______.
aminoacyl tRNA; A site
Identify the lagging strand in the figure.
c
After chromosomes condense, the _____________ is the region where the identical DNA molecules are most tightly attached to each other.
centromere
The ______ are the organizing centers for microtubules involved in separating chromosomes during mitosis.
centrosomes
During interphase, most of the nucleus is filled with a complex of DNA and protein in a dispersed form called _______.
chromatin
In most eukaryotes, division of the nucleus is followed by ______, when the rest of the cell divides.
cytokinesis
Sort the phrases depending on which protein they describe. Proteins: helicase, topoisomerase, single-strand binding protein Phrases: binds ahead of replication fork, binds at the replication fork, binds after the replication fork, prevents H-bonds between bases, breaks H-bonds between bases, breaks covalent bonds in DNA backbone
helicase: binds at replication fork, breaks H-bonds between bases topoisomerase: binds ahead of the replication fork, breaks covalent bonds in DNA backbone single-strand binding protein: prevents H-bonds between bases
In dividing cells, most of the cell's growth occurs during _________.
interphase
During mitosis, microtubules attach to chromosomes at the ____________.
kinetochores