Bio 191 Ch. 16

Desktop Ch. 16 1 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 "heavy" (radioactive) nitrogen (15N) for several generations and then transfer them to 14N medium. Which pattern in the figure would you expect if the DNA was replicated in a conservative manner? A B C D

B

A sample of double-stranded DNA contains 28% thymine. Approximately what percent of the nucleotides in this sample will be guanine? 16% 22% 8% 72%

22%

The sequence of nucleotides below is present at a DNA location where the chain opens to form a replication fork:3' C C T A G G C T G C A A T C C 5'An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence? 5' A C G T T A G G 3' 5' A C G U U A G G 3' 5' A G C C U A G G 3' 5' A G C C T A G G 3'

5' A C G U U A G G 3'

Desktop Ch. 16 2 Referring to the figure, what bases will be added as DNA replication proceeds on the bottom strand? 5′ C, A, G, C, A, G, A 3′ 3′ G, T, C, G, T, C, T 5′ 3′ T, C, T, G, C, T, G 5′ 5′ A, G, A, C, G, A, C 3′

5′ A, G, A, C, G, A, C 3′

A sample of double-stranded DNA contains 42% cytosine. Approximately what percent of the nucleotides in this sample will be thymine? 42% 8% 58% 16%

8%

Which of the following combinations of base pairs will be found in a molecule of DNA? A = G and C = T A + C = G + T G + C = T + A A = C

A + C = G + T

DNA strands are antiparallel. Which of the following statements defines "antiparallel"? The double helix structure of DNA creates nonparallel strands. One DNA strand contains bases that complement the bases in the opposite strand. Hydrogen bonds between base pairs cause DNA strands to cross. A 5' to 3' DNA strand is paired with the 3' to 5' DNA strand.

A 5' to 3' DNA strand is paired with the 3' to 5' DNA strand.

Which of the following is a reason that the low error rate of DNA replication is important to evolution? Replication with a high error rate is likely to kill the cell. Most mutations have no effect on phenotype. Rare errors are the source of variation. Fixing replication errors provides a cellular role for mismatch repair enzymes.

Rare errors are the source of variation.

Which of the following is most likely to result from reduced or very little active telomerase activity? Cells age and begin to lose function. Cells maintain normal functioning. Cells may become cancerous. Telomere lengthens in germ cells.

Cells age and begin to lose function.

Exposure to the UV radiation in sunlight causes DNA changes in skin cells. Why are these changes more harmful when they occur in an individual with xeroderma pigmentosum (XP) than in an individual who does not have this disorder? Compared to XP individuals, non-XP individuals produce more UV protecting pigments. XP individual's DNA replication machinery incorporates more incorrect nucleotides in new DNA strands than occur in non-XP individuals. Compared to XP individuals, non-XP individuals have more effective nucleotide excision repair enzymes. XP individuals have significantly more thymine's in their DNA than non-XP individuals do

Compared to XP individuals, non-XP individuals have more effective nucleotide excision repair enzymes.

Desktop Ch. 16 1 In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" (radioactive) nitrogen (15N) and then transferred them to a medium containing 14N (non-radioactive). Which of the results in the figure would be expected after one round of DNA replication in the presence of 14N? A B C D

D

Frederick Griffith heat-killed a culture of pathogenic bacteria. He split the sample and injected half of it into mice. The mice lived. He then mixed the other half with a living, nonpathogenic bacteria strain and injected the mixture into mice. The mice died. These results best support which of the following conclusions. A. non-pathogenic bacteria were transformed by pathogenic capsule proteins B. the initial heat treatment was unsuccessful C. splitting the culture revived the pathogenic bacteria D. a substance had been transferred from pathogenic to nonpathogenic bacteria

D. a substance had been transferred from pathogenic to nonpathogenic bacteria

A phosphorescent red strain of bacteria is heat-killed and mixed with a living, colorless strain. Further observations of the mixture show that some of the living cells are now red. Which of the following observations would provide the best evidence that red color is a heritable trait? A. after a few generations there are no more colorless cells, all cells are red B. when the heat-killed and living cells are mixed there is a decrease in the overall amount of red color C. especially bright red color in some members of the living strain D. as the living cells divide the number of red cells increases

D. as the living cells divide the number of red cells increases

Hershey and Chase set out to determine which type of molecule is used for genetic inheritance. They completed a series of experiments where E. coli was infected by a T2 virus. Which molecular component of the T2 virus ended up inside the cell? RNA ribosome protein DNA

DNA

Which of the following characteristics allowed Hershey and Chase to determine whether the genetic material was made of DNA or protein? DNA contains purines, whereas protein includes pyrimidines. DNA contains nitrogen, whereas protein does not. DNA contains sulfur, whereas protein does not. DNA contains phosphorus, whereas protein does not.

DNA contains phosphorus, whereas protein does not.

Radioactive thymine is added to media containing one actively dividing E. coli bacterium. Which of the following outcomes would be seen after a single cell division? One of the daughter cells, but not the other, would have radioactive DNA. Neither of the two daughter cells would be radioactive. DNA in both daughter cells would be radioactive. All four bases of the DNA would be radioactive.

DNA in both daughter cells would be radioactive.

In bacteria, which of the following proteins is responsible for removing nucleotides from the RNA primer that is used for initiation DNA synthesis? DNA ligase DNA pol III Primase DNA pol I

DNA pol I

What catalyzes the formation of phosphodiester bonds between a DNA strand and a new nucleotide being added during DNA replication? Helicase Primase DNA polymerase ATP

DNA polymerase

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

DNA polymerase III

The lagging strand is characterized by a series of short segments of DNA (Okazaki fragments) that are 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 is the genetic material that requires removal of short RNA segments to be functional. DNA is a polymer consisting of four monomers: adenine, thymine, guanine, and cytosine. Bacterial replication is fundamentally different from eukaryotic replication. DNA polymerase synthesizes leading and lagging strands during replication only in one direction.

DNA polymerase synthesizes leading and lagging strands during replication only in one direction.

After DNA replication, the resulting daughter DNA double helix contains one strand of the original parental DNA and one new strand. What is the explanation for this phenomenon? DNA replication is conservative. RNA synthesis is conservative. DNA replication is not conservative. DNA replication is semiconservative.

DNA replication is semiconservative.

Which of the following is a reason that a new DNA strand elongates only in the 5' to 3' direction during DNA replication? Dehydration reactions require a free -OH group. DNA polymerase begins adding nucleotides at the 3' end of the template. Replication must progress toward the replication fork. Single stranded binding protein stabilizes DNA by blocking access to the 5' end.

Dehydration reactions require a free -OH group.

Which of the following investigators was (were) responsible for determining that DNA contains equal amounts of adenine and thymine, and equal amounts of guanine and cytosine? Oswald Avery, Maclyn McCarty, and Colin MacLeod Erwin Chargaff Alfred Hershey and Martha Chase Matthew Meselson and Franklin Stahl

Erwin Chargaff

Which of the following statements describes the process of transformation in bacteria? A strand of RNA is created from a DNA molecule. Bacterial cells are infected by a phage DNA molecule. A strand of DNA is created from an RNA molecule. External DNA is taken into a cell, becoming part of the cell's genome.

External DNA is taken into a cell, becoming part of the cell's genome.

Which of the following statements correctly describes the structure of chromatin? Euchromatin is not transcribed, whereas heterochromatin is transcribed. Heterochromatin is composed of DNA, whereas euchromatin is made of DNA and RNA. Heterochromatin is highly condensed, whereas euchromatin is less compact. Both heterochromatin and euchromatin are found in the cytoplasm.

Heterochromatin is highly condensed, whereas euchromatin is less compact.

Which of the following structural characteristics is most critical for the association between histones and DNA? There are at least five different histone proteins in every eukaryote. Histones are small proteins. Histones are positively charged. Histones are highly conserved (that is, histones are very similar in every eukaryote).

Histones are positively charged.

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

It joins Okazaki fragments together.

Within a double-stranded DNA molecule, if adenine forms hydrogen bonds with thymine, and cytosine forms hydrogen bonds with guanine what consequence in the structure of the DNA? It allows variable width of the double helix. It determines the tertiary structure of a DNA molecule. It permits complementary base pairing. It determines the type of protein produced.

It permits complementary base pairing.

Who performed classic experiments that supported the semiconservative model of DNA replication? Watson and Crick Franklin and Wilkins Hershey and Chase Meselson and Stahl

Meselson and Stahl

In E. coli, a mutation in a gene called dnaB prevents the helicase from binding at the origin of replication. Which of the following events would you expect to occur as a result of this mutation? Replication will require a DNA template from another source. No replication fork will be formed. Replication will occur via RNA polymerase alone. Additional proofreading will occur.

No replication fork will be formed.

A replication error results in a zygote that has inactive telomerase, which of the following characteristics would you expect to see in the organism that develops? a reduction in chromosome length in gametes an inability to repair thymine dimers a high probability of somatic cells becoming cancerous an inability to produce Okazaki fragments

a reduction in chromosome length in gametes

Frederick Griffith heat-killed a culture of pathogenic bacteria. He split the sample and injected half of it into mice. The mice lived. He then mixed the other half of the sample with a living, nonpathogenic bacteria strain and injected the mixture into mice. The mice died. Which of the following describes a treatment that would help clarify interpretation of these data? examining tissue from the dead mice (injected with mixed sample) for the presence of pathogenic bacteria culturing bacteria from blood isolated from the living mice (injected with heat-killed pathogenic bacteria) injecting another population of mice with the original, heat-killed pathogenic bacteria heat killing the mixed sample and injecting it into mice

examining tissue from the dead mice (injected with mixed sample) for the presence of pathogenic bacteria

DNA is isolated from bacteria undergoing DNA replication. After heat treatment to disrupt H-bonds the DNA is centrifuged and it separates into two classes. One class of 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). Which types of DNA do the two classes most likely represent? lagging strands and Okazaki fragments leading strands and fragments generated due to replication errors leading strands and Okazaki fragments Okazaki fragments and Origin of replication

leading strands and Okazaki fragments

In DNA replication in E. coli, the enzyme primase is used to attach a 5 to 10 base ribonucleotide strand complementary to the parental DNA strand. The RNA strand serves as a starting point for the DNA polymerase that replicates the DNA. If a mutation occurred in the primase gene, which of the following results would you expect? Replication would not be affected as the enzyme primase in involved with RNA synthesis. Replication would only occur on the leading strand. Replication would not occur on either the leading or lagging strand. Replication would only occur on the lagging strand.

Replication would not occur on either the leading or lagging strand.

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. Which of the following best explains the effect of telomerase on cellular aging? Telomerase will speed up the rate of cell proliferation. Telomerase shortens telomeres, which delays cellular aging. Telomerase can eliminate telomere shortening and slows aging. Telomerase would have no effect on cellular aging.

Telomerase can eliminate telomere shortening and slows aging.

Which of the following statements correctly describes the difference between the leading strand and the lagging strand in DNA replication? 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. 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 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.

Which of the following statements correctly describes the difference between the leading and the lagging strands of DNA in DNA replication? 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 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 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 at twice the rate of the lagging strand.

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 of the following statements correctly describes the difference between ATP used in metabolism and the nucleotides used as a building block during DNA synthesis? ATP contains three high-energy bonds; the nucleotides have two. The nucleotides have two phosphate groups; ATP has three phosphate groups. ATP is found only in human cells; the nucleotides are found in all animal and plant cells. The nucleotides have the sugar deoxyribose; ATP has the sugar ribose.

The nucleotides have the sugar deoxyribose; ATP has the sugar ribose.

Researchers found a strain of bacteria that had mutation rates one hundred times higher than normal. Which of the following statements correctly describes the most likely cause of these results? There were one or more base pair mismatches in the RNA primer. The single-strand binding proteins were malfunctioning during DNA replication. The DNA polymerase was unable to add bases to the growing nucleic acid chain. The proofreading mechanism of DNA polymerase was not working properly.

The proofreading mechanism of DNA polymerase was not working properly.

Two students decided to repeat the Hershey and Chase experiment, with modifications. Like Hershey and Chase they used radioactive sulfur but they substituted radioactive nitrogen for radioactive phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogen atoms. Thus, labeling the nitrogen atoms would provide a stronger signal than labeling the phosphates. Which of the following is the biggest shortcoming in their experimental design? There is no radioactive isotope of nitrogen. The radioactivity would not distinguish between DNA and proteins because proteins contain nitrogen. The signal from the nucleotide would be so strong that it would overwhelm the signal from sulfur. Radioactive nitrogen has a half-life of 100,000 years, therefore, the material would be too dangerous for too long.

The radioactivity would not distinguish between DNA and proteins because proteins contain nitrogen.

Semiconservative replication involves a template. Which of the following best describes the template molecule? an RNA molecule DNA polymerase single-stranded binding proteins one strand of the DNA molecule

one strand of the DNA molecule

Which of the following types of cells are affected most by telomere shortening? only eukaryotic cells only animal cells only plant cells only prokaryotic cells

only eukaryotic cells

What is the function of the enzyme topoisomerase in DNA replication? relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix detecting the shape of the template base's surface to help recruit the appropriate nucleotide to pair building RNA primers using the parental DNA strand as a template reattaching the hydrogen bonds between the base pairs in the double helix

relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix

Which of the following characteristics of DNA allows it to carry a vast amount of hereditary information? complementary pairing of bases antiparallel orientation phosphate-sugar backbones sequence of bases

sequence of bases

Which of the following types of molecules help to hold the DNA strands apart while they are being replicated? ligase primase DNA polymerase single-strand DNA binding proteins

single-strand DNA binding proteins

In DNA polymerization, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and which of the following atoms or molecules of the last nucleotide in the polymer? the 3' OH a nitrogen from the nitrogen-containing base C6 the 5' phosphate

the 3' OH

In a healthy eukaryotic cell, the rate of DNA repair is typically equal to the rate of DNA mutation. Which of the following is most likely to result if the rate of repair lags behind the rate of mutation? RNA may be used instead of DNA as inheritance material the cell can be transformed into a cancerous cell DNA replication will proceed more quickly DNA replication will continue by a new mechanism

the cell can be transformed into a cancerous cell

Which of the following is most likely to result if a cell is unable to produce histone proteins? the 30-nm fiber pack more tightly and become thinner than 30 nm topoisomerases in the 300-nm fiber scaffolding would not need to be as active there would be an increase in the amount of DNA produced during replication the cell's DNA could not be packed into its nucleus

the cell's DNA could not be packed into its nucleus

What are telomeres? the ends of linear chromosomes the structures that hold two sister chromatids together the sites of origin of DNA replication enzymes that elongate the DNA strand during replication

the ends of linear chromosomes

Histone proteins contain internal cores that are hydrophobic and surface amino acids that are positively charged. Which of the following characteristics of DNA would best support tight binding between DNA and histones? the 3.4 nm per helical turn in DNA fits around the spherical shape of the histones the DNA backbone has a net negative charge that forms ionic bonds with histones the ring structures in DNA bases that disperse charge promote hydrophobic interactions with histone cores DNA 5' and 3' ends have negative charge responsible for stabilizing interactions with histone surfaces

the ring structures in DNA bases that disperse charge promote hydrophobic interactions with histone cores

In bacteria, what is the function of DNA polymerase III? to seal together the broken ends of DNA strands to degrade damaged DNA molecules to unwind the DNA helix during replication to add nucleotides to the 3' end of a growing DNA strand

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

Which of the following statements accurately describes the structure of a eukaryotic chromosome? It has different numbers of genes in different cell types of an organism. It is a single linear molecule of double-stranded DNA plus proteins. It is constructed as a series of nucleosomes wrapped around two DNA molecules. It is composed of a single strand of DNA.

It is a single linear molecule of double-stranded DNA plus proteins.

Which answer best describes the role of telomerase in replicating the ends of linear chromosomes? It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity. It adds a 5' cap structure to the chromosome ends that resists degradation by nucleases. It adds numerous GC pairs, which resist hydrolysis and maintain chromosome integrity. 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.

Which answer best describes the role of telomerase in replicating the ends of linear chromosomes? It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity. It adds a 5' cap structure to the chromosome ends that resists degradation by nucleases. It adds numerous GC pairs, which resist hydrolysis and maintain chromosome integrity. 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.

Which of the following statements accurately describes differences between DNA replication in prokaryotes and DNA replication in eukaryotes? 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. Prokaryotic chromosomes have histones, whereas eukaryotic chromosomes do not.

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

Rosalind Franklin's X-ray crystallography data suggested DNA is double stranded and has a uniform diameter. These observations can be used to rule out base pairing between two of the same nucleotide because ________. an A-A pair is wider than a C-C pair thymine dimers are removed by excision repair the antiparallel orientation of strands would result in one of the pair being upside down identical nucleotides would not have the appropriate number of hydrogen bonding sites to pair

an A-A pair is wider than a C-C pair

Which list the provides the correct enzyme order required for nucleotide excision repair of a thymine dimer? nuclease, DNA polymerase, RNA primase nuclease, DNA polymerase, DNA ligase DNA ligase, nuclease, helicase helicase, DNA polymerase, DNA ligase

nuclease, DNA polymerase, DNA ligase

Which of the following lists represents the order of increasingly higher levels of organization of chromatin? nucleosome, 30-nm chromatin fiber, looped domain nucleosome, looped domain, 30-nm chromatin fiber looped domain, 30-nm chromatin fiber, nucleosome 30-nm chromatin fiber, nucleosome, looped domain

nucleosome, 30-nm chromatin fiber, looped domain