Exam 3 Review 3 04/21/17

Art Questions

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

2) 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 15 N medium for several generations and then transfer them to 14 N medium. Which pattern in the figure above would you expect if the DNA was replicated in a conservative manner?
A) A
B) B
C) C
D) D
E) E

3) Once the pattern found after one round of replication was observed, Meselson and Stahl could be confident of which of the following conclusions?
A) Replication is semi-conservative.
B) Replication is not dispersive.
C) Replication is not semi-conservative.
D) Replication is not conservative.
E) Replication is neither dispersive nor conservative.

Use the following list of choices for the following questions:

I. helicase II. DNA polymerase III III. L igase IV. DNA polymerase I
V. primase

4) Which of the enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?
A) I B) II C) III D) IV E) V

5) Which of the enzymes separates the DNA strands during replication?
A) I
E) V

6) Which of the enzymes covalently connects segments of DNA?
A) I
E) V

7) Which of the enzymes synthesizes short segments of RNA?
A) I
E) V

8) Which of the following sets of materials are required by both eukaryotes and prokaryotes for replication?
A) double-stranded DNA, four kinds of dNTPs, primers, origins
B) topoisomerases, telomerases, polymerases
C) G-C rich regions, polymerases, chromosome nicks
D) nucleosome loosening, four dNTPs, four rNTPs
E) ligase, primers, nucleases

9) Which of the following help(s) to hold the DNA strands apart while they are being replicated?
A) primase
B) ligase
C) DNA polymerase
D) single-strand binding proteins
E) exonuclease

10) What is the function of topoisomerase?
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) adding methyl groups to bases of DNA
D) unwinding of the double helix
E) stabilizing single-stranded DNA at the replication fork

11) What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?
A) It synthesizes RNA nucleotides to make a primer.
B) It catalyzes the lengthening of telomeres.
C) It joins Okazaki fragments together.
D) It unwinds the parental double helix.
E) It stabilizes the unwound parental DNA.

12) To repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?
A) exonuclease, DNA polymerase III, RNA primase
B) helicase, DNA polymerase I, DNA ligase
C) DNA ligase, nuclease, helicase
D) DNA polymerase I, DNA polymerase III, DNA ligase
E) endonuclease, DNA polymerase I, DNA ligase

13) What is the function of DNA polymerase III?
A) to unwind the DNA helix during replication
B) to seal together the broken ends of DNA strands
C) to add nucleotides to the 3' end of a growing DNA strand
D) to degrade damaged DNA molecules
E) to rejoin the two DNA strands (one new and one old) after replication

14) The DNA of telomeres has been found to be highly conserved throughout the evolution of eukaryotes. What does this most probably reflect?
A) the inactivity of this DNA
B) the low frequency of mutations occurring in this DNA
C) that new evolution of telomeres continues
D) that mutations in telomeres are relatively advantageous
E) that the critical function of telomeres must be maintained

15) The enzyme telomerase solves the problem of replication at the ends of linear chromosomes by which method?
A) adding a single 5' cap