chapter 16 study guide

In a nucleosome, the DNA is wrapped around: (A) histones (B) ribosomes (C) polymerase molecules (D) a thymine dimer

(A) histones The negatively charged phosphate groups in DNA are tightly bound to the positively charged histones.

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 (B) telomerase, primase, DNA polymerase (C) telomerase, helicase, single-strand binding protein (D) DNA ligase, replication fork proteins, adenylyl cyclase

(A) nuclease, DNA polymerase, and DNA ligase. Nuclease: enzyme that cleaves the nucleotides in nucleic acids into smaller units DNA polymerase: enzyme that synthesizes DNA molecules Ligase: enzyme that brings about ligation (surgical process of "tying up" things together) with DNA or another molecule

In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules? (A) A = G (B) A + G = C + T (C) A + T = G + C (D) A = C

(B) A + G = C + T The amount of A = T, while the amount of G = C. A = T = 40 G = C = 30 40 + 30 = 30 + 40

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? (A) DNA polymerase (B) DNA ligase (C) Okazaki fragments (D) primase

(B) DNA ligase DNA ligase connects the Okazaki fragments; since the segments of DNA are a "few hundred nucleotides long", she has probably forgotten to connect them. Since replication was done, DNA polymerase and primase should have been in the mixture.

Evidence to support that DNA strands run antiparallel to each other includes all of the following except __________. (A) Chargaff's rules (B) that the sugar-phosphate backbones are to the inside of the molecule (C) hydrogen bonding interactions (D) X-ray measurement data (E) that the nitrogenous bases are on the inside

(B) that the sugar-phosphate backbones are to the inside of the molecule Sugar-phosphate backbones are on the outside of the DNA molecule.

When __________ form after an exposure to ultraviolet (UV) light, a __________ can remove the damaged nucleotides and replace them with normal nucleotides. (A) guanosine dimers; nucleotide incision repair enzyme (B) thymidine dimers; nucleotide incision repair enzyme (C) cytosine dimers; nucleotide excision repair enzyme (D) thymidine dimers; nucleotide excision repair enzyme (E) guanosine dimers; nucleotide excision repair enzyme

(B) thymidine dimers; nucleotide incision repair enzyme UV exposure causes 2 thymine bases that are next to each other on the same DNA strand to covalently link and form a ink that interferes with DNA replication.

DNA polymerase adds nucleotides to the __________ of the leading strands, and to the __________ of the lagging strands (Okazaki fragments). (A) 3' end; 5' end (B) sugar group; phosphate group (C) 3' end; 3' end (D) 5' end; 3' end (E) 5' end; 5' end

(C) 3' end; 3' end DNA polymerase adds nucleotides to the 3' end of the leading strands, and to the 3' end of the lagging strands (Okazaki fragments). DNA polymerase can only add nucleotides to the 3' end of a growing strand.

Which of the following statements is correct? (A) Adenine forms three covalent bonds with thymine; guanine forms two covalent bonds with cytosine. (B) Adenine forms three hydrogen bonds with thymine; guanine forms two hydrogen bonds with cytosine. (C) Adenine forms two hydrogen bonds with thymine; guanine forms three hydrogen bonds with cytosine. (D) Adenine forms two covalent bonds with thymine; guanine forms three covalent bonds with cytosine. (E) Adenine forms two hydrogen bonds with guanine; thymine forms three hydrogen bonds with cytosine.

(C) Adenine forms two hydrogen bonds with thymine; guatanine forms three hydrogen bonds with cytosine. The bases are connected to each other through hydrogen bonds, not covalent. A to T, C to G.

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized? (A) The origins of replication occur only at the 5′ end. (B) Helicases and single-strand binding proteins work at the 5′ end. (C) DNA polymerase can join new nucleotides only to the 3′ end of a pre-existing strand, and the strands are antiparallel. (D) DNA ligase works only in the 3′ -> 5′ direction.

(C) DNA polymerase can join new nucleotides only to the 3' end of a pre-existing strand, and the strands are antiparallel. The leading strand is the new, replicated strand. Its directionality is 5' => 3'. Since it is antiparallel, the other new strand (lagging) has to be faced "away" (starts at the 3' end).

In his work with pneumonia-causing bacteria and mice, Griffith found that (A) the protein coat from pathogenic cells was able to transform non-pathogenic cells. (B) heat-killed pathogenic cells caused pneumonia. (C) some substance from pathogenic cells was transferred to non-pathogenic cells, making them pathogenic. (D) the polysaccharide coat of bacteria caused pneumonia.

(C) Some substance from pathogenic cells were transferred to non-pathogenic cells, making them pathogenic. Heat doesn't kill all the bacteria away; it adapts and resists and will transfer on to non-pathogenic cells.

The elongation of the leading strand during DNA synthesis ' (A) progresses away from the replication fork. (B) occurs in the 3′ => 5′ direction. (C) produces Okazaki fragments. (D) depends on the action of DNA polymerase

(D) Depends on the action of the DNA polymerase. All the other actions (A, B, and C) occur with lagging strands.

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? (A) one high-density and one low-density band (B) one intermediate-density band (C) one high-density and one intermediate-density band (D) one low-density and one intermediate-density band

(D) One low-density and one intermediate-density band. DNA replicates semiconservatively, meaning they replicate with one old DNA and one new DNA strand. N15 is heavier than N14; therefore, DNA having more N15 content will form high-density band in centrifugation. First generation: E. coli with both 15N (old) and 14N (new). This creates the intermediate-density band. Second generation: DNA will replicate again, which is similar to the parent. Old 14N with new 14N = 100% 14N (low density, compared to the heavy 15N). A 100% 15N would be a high-density band.

The two sugar-phosphate strands that form the rungs of a DNA double helix are joined to each other through __________. (A) 5' deoxyribose and phosphate bonds (B) covalent bonds between nitrogen atoms in adenine and in thymine (C) covalent bonds between carbon atoms in deoxyribose molecules (D) hydrogen bonds between nucleotide bases (E) ionic bonds between guanine and cytosine

(D) hydrogen bonds between nucleotide bases The rungs are the nucleotide bases on the inside of the DNA molecule.

The information in DNA is contained in __________. (A) the variation in the structure of nucleotides that make up the DNA molecule (B) the sequence of amino acids that makes up the DNA molecule (C) All of the listed responses are correct (D) the sequence of nucleotides along the length of the two strands of the DNA molecule (E) the types of sugars used in making the DNA molecule

(D) the sequence of nucleotides along the length of the two strands of the DNA molecule The nucleotides (nitrogenous bases) code for the genes in the DNA.

The information in DNA is contained in _____. (A) the sequence of amino acids that makes up the DNA molecule (B) the types of sugars used in making the DNA molecule (C) the variation in the structure of nucleotides that make up the DNA molecule (D) the sequence of nucleotides along the length of the two strands of the DNA molecule (E) All of the listed responses are correct.

(D) the sequence of nucleotides along the length of the two strands of the DNA molecule. two strands = double helix. sequence of nucleotides (aa) that make up the DNA molecule.

Which set of enzymes is involved in nucleotide excision repair? (A) nuclease, DNA polymerase, primase (B) nuclease, DNA polymerase, primase (C) ligase, nuclease, and primase (D) hydrolase, nuclease, and ligase (E) DNA polymerase, helicase, primase (F) nuclease, DNA polymerase, and ligase

(F) nuclease, DNA polymerase, and ligase Nuclease: enzyme that cleaves the nucleotides in nucleic acids into smaller units DNA polymerase: enzyme that synthesizes DNA molecules Ligase: enzyme that brings about ligation (surgical process of "tying up" things together) with DNA or another molecule