bio chapter 16
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
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
In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the 5' → 3' direction?
Selected Answer: DNA polymerase III
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
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
Telomere shortening is a problem in which types of cells?
Selected Answer: only eukaryotic cells
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.
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
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.
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.
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 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
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
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