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Exam 3 Review 3 04/21/17
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?
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?
3) Once the pattern found after one round of replication was observed, Meselson and Stahl could be confident of which of the following conclusions?
D) Replication is not conservative .
Use the following list of choices for the following questions:
I. helicase II. DNA polymerase III III. L igase IV. DNA polymerase I
4) Which of the enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?
D) DNA polymerase I
5) Which of the enzymes separates the DNA strands during replication?
A) I (Helicase II)
6) Which of the enzymes covalently connects segments of DNA?
C) III (Ligase IV)
7) Which of the enzymes synthesizes short segments of RNA?
E) V (Primase)
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
9) Which of the following help(s) to hold the DNA strands apart while they are being replicated?
D) single-strand binding proteins
10) What is the function of topoisomerase?
A) relieving strain in the DNA ahead of the replication fork
11) What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?
C) It joins Okazaki fragments together.
12) To repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?
E) endonuclease, DNA polymerase I, DNA ligase
13) What is the function of DNA polymerase III?
C) to add nucleotides to the 3' end of a growing DNA strand
14) The DNA of telomeres has been found to be highly conserved throughout the evolution of eukaryotes. What does this most probably reflect?
D) that mutations in telomeres are relatively advantageous
15) The enzyme telomerase solves the problem of replication at the ends of linear chromosomes by which method?
D) adding numerous short DNA sequences such as TTAGGG, which form a hairpin turn
16) In E. coli , there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?
B) No replication fork will be formed.
17) Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?
B) DNA ligase
C) DNA polymerase III
18) In his transformation experiments, what did Griffith observe?
B) Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.
19) How do we describe transformation in bacteria?
E) assimilation of external DNA into a cell
20) After mixing a heat-killed, phosphorescent strain of bacteria with a living nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observations would provide the best evidence that the ability to fluoresce is a heritable trait?
D) Descendants of the living cells are also phosphprescent
21) In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?
B) DNA contains phosphorus, whereas protein does not.
22) Which of the following investigators was/were responsible for the following discovery?
In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.
D) Erwin Chargaff
23) Cytosine makes up 42% of the
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