Unit 6 part 1

The DNA of an organism has thymine as 20% of its bases. What percentage of its bases would be guanine? Select one: a. 20% b. 40% c. 30% d. 80% e. 60%

30%

At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork: 3' CCTAGGCTGCAATCC 5' An RNA primer is formed starting at the underlined T of the template. Which of the following represents the primer sequence? Select one: a. 5' ACGUUAGG 3' b. 5' ACGTTAGG 3' c. 5' GCCTAGG 3' d. 5' GCCUAGG 3'

5' ACGUUAGG 3'

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? Select one: a. 42% b. 16% c. 58% d. 8%

8%

Refer to the figure above. What bases will be added to the primer as DNA replication proceeds? The bases should appear in the new strand in the order that they will be added starting at the 3' end of the primer. Select one: a. A,G,A,C,G,A,C b. G,T,C,G,T,C,T c. T,C,T,G,C,T,G d. C,A,G,C,A,G,A

A,G,A,C,G,A,C

In E. coli, which enzymes catalyzes the elongation of a new DNA strand in the 5' → 3' direction Select one: a. DNA ligase b. primase c. DNA polymerase III d. helices

DNA polymerase III

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? Select one: a. Bacterial replication is fundamentally different from eukaryotic replication. The key shouldn't be way longer than the distractors. b. DNA polymerase is a directional enzyme that synthesizes leading and lagging strands during replication. c. DNA is a polymer consisting of four monomers: adenine, thymine, guanine, and cytosine d. DNA is the genetic material

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

Use the following list of choices for the following questions I. helicase II. DNA polymerase III III. ligase IV. DNA polymerase I V. primase Which of the enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments? Select one: a. V b. I c. IV d. III e. II

IV

How does DNA synthesis along the lagging strand differ from that on the leading strand? Select one: a. nucleotides are added to the 5' end instead of the 3' end b. ligase is the enzyme that polymerizes DNA on the lagging strand c. Okazaki fragments, which each grow 5'-3', must be joined along the lagging strand d. helicase synthesizes Okazaki fragments, which are then joined by ligase e. An RNA primer is needed on the lagging strand but not on the leading strand Feedback

Okazaki fragments, which each grow 5'-3', must be joined along the lagging strand

In E. coli replication 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 would you expect? Select one: a. Replication would not occur on either the leading or lagging strand. b. Replication would not be affected as the enzyme primase involved with RNA synthesis. c. Replication would only occur on the leading strand. d. Replication would only occur on the lagging strand.

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

At which letter would the next nucleotide be added? a. A b. G c. T

T

What is the difference between the leading strand and the lagging strand in DNA replication? Select one: 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. There are different DNA polymerases involved in elongation of the leading strand and the lagging strand d. The leading strand is synthesized continuously in the 5' → 3' direction, while the lagging strand is synthesized discontinuously in the 5' →3' direction. Feedback

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

Researchers found E. coli that had mutation rates one hundred times higher than normal. Which of the following is the most likely cause of these results? Select one: a. The proofreading mechanism of DNA polymerase was not working properly. b. The single-stranded binding proteins were malfunctioning c. The DNA polymerase was unable to add bases to the 3' end of the growing nucleic acid chain. d. There were one or more mismatches in the RNA primer.

The proofreading mechanism of DNA polymerase was not working properly.

Use the following list of choices for the following questions I. helicase II. DNA polymerase III III. ligase IV. DNA polymerase I V. primase Which of the enzymes synthesizes short segments of RNA? Select one: a. III b. IV c. I d. V e. II

V

Which of the following would you expect of a eukaryote lacking telomerase? Select one: a. a high probability of somatic cells becoming cancerous b. a reduction in chromosome length in gametes c. production of Okazaki fragments d. high sensitivity to sunlight e. inability to repair thymine dimers

a reduction in chromosome length in gametes

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

a single linear molecule of double stranded DNA plus proteins

In their classic experiment, Meselson and Stahl

a. provided evidence for the semiconservative model of DNA replication

BLANK are weak bonds that hold the two strands of DNA together, but also allow DNA to separate and replicate. The tips of chromosomes are known as BLANK

hydrogen bonds and telemers

Which of the following statements describes the eukaryotic chromosome? Select one: a. it consists of a single linear molecule of double-stranded DNA plus proteins b. the nucleosome is its most basic functional subunit c. it is composed of DNA alone d. active transcription occurs on heterochromatin bot not euchromatin e. the number of genes on each chromosome is different in different cell types of an organism

it consists of a single linear molecule of double-stranded DNA plus proteins

Which of the following statements about DNA polymerase is incorrect? Select one: a. it is unable to initiate synthesis; it requires an RNA primer b. it forms the bonds between complementary base pairs c. it only works in the 5'-3' direction d. it is found in eukaryotes and prokaryotes e. it is able to proofread and correct errors in base pairing

it forms the bonds between complementary base pairs

The structure labeled "X" is a(n)

nucleotide

The continuous elongation of a new DNA strand along one of the template strands Select one: a. requires the action of DNA ligase as well as polymerase. b. occurs because DNA ligase can only elongate in the 5'-3' direction. c. occurs on the leading strand. d. occurs on the lagging strand.

occurs on the leading strand.

Which of the following enzymes or proteins is paired with an incorrect or inaccurate function? Select one: a. primase- forms DNA primer to start replication b. nuclease-cuts out (excises) damaged DNA strands c. single-strand binding protein-holds strands of unwound DNA apart and straight d. helicase- unwinds and separates parental double helix e. telomerase- adds telomere repetitions to ends of chromosomes

primase- forms DNA primer to start replication

Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons? Select one: a. prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many b. the rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes c. prokaryotes produce Okazaki fragments during DNA replication, but eukaryotes do not d. prokaryotic chromosomes have histones, whereas eukaryotic chromosomes do not.

prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many

What is the function of topoisomerase? Select one: a. relieving strain in the DNA ahead of the replication fork b. elongating new DNA at a replication fork by adding nucleotides to the existing chain c. stabilizing single-stranded DNA at the replication fork d. unwinding of the double helix

relieving strain in the DNA ahead of the replication fork

DNA is synthesized through a process known as___ Select one: a. translation b. conservative replication c. semiconservative replication d. transcription

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? Select one: a. complementary pairing of bases b. side groups of nitrogenous bases c. phosphate-sugar backbones d. sequence of bases

sequence of bases

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

t catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity.

What is meant by the description "antiparallel" regarding the strands that make up DNA? Select one: a. one strand is positively charged and the other is negatively charged b. the twisting nature of DNA creates nonparallel strands c. the 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand d. base pairings create unequal spacing between the two DNA strands e. one strand contains only purines and the other contains only pyrimidines

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

The joining of nucleotides in the polymerization of DNA requires energy from Select one: a. DNA polymerase b. RNA nucleotides c. the hydrolysis of the pyrophosphates removed from nucleoside triphosphate d. the phosphate groups of the sugar-phosphate backbone e. the hydrolysis of the terminal phosphate group of ATP

the hydrolysis of the pyrophosphates removed from nucleoside triphosphate

Watson and Crick concluded that each base could not pair with itself because Select one: a. identical bases could not hydrogen-bond together b. the uniform width of 2nm would not permit two purines or two pyrimidines to pair together c. the bases could not be stacked 0.34 nm apart d. there would not be room for the helix to make a full turn every 3.4 nm e. they would be on antiparallel stands

the uniform width of 2nm would not permit two purines or two pyrimidines to pair together

Which of the following statements about telomeres is correct? Select one: a. they are repetitive sequences of nucleotides at the centromere region of a chromosome b. they are ever-shortening tips of chromosomes that may signal cells to stop dividing at maturity and they are highly repetitive sequences at the tips of chromosomes that protect the lagging strand during replication c. they are enzymes, in germ cells that allow these cells to undergo repeated divisions d. they are ever-shortening tips of chromosomes that may signal cells to stop dividing at maturity e. they are highly repetitive sequences at the tips of chromosomes that protect the lagging strand during replication

they are ever-shortening tips of chromosomes that may signal cells to stop dividing at maturity and they are highly repetitive sequences at the tips of chromosomes that protect the lagging strand during replication