MOLECULAR GENETICS
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DNA Replication
1. Without proofreading by DNApol during DNA replication, there would be too many
mutations for a cell to survive very many rounds of replication. (T/F)
2. Thymine dimers occur when DNA is exposed to gamma radiation or x-rays. (T/F)
3. DNA replication starts at the origin, which is always located near the 5’ end of the sense
strand. (T/F)
4. To form double stranded DNA, purines hydrogen bond with purines while pyrimidines
hydrogen bond pyrimidines. (T/F)
5. DNA polymerase not only attaches new nucleotides to the growing strand, it also proofreads
and corrects mistakes made when incorrect nucleotides are occasionally inserted. (T/F)
6. DNA repair mechanisms will usually not be able to fix mutations once the DNA has
undergone replication. (T/F)
7. Bacterial RNA polymerase is composed of the catalytically active core enzyme and a
separable sigma factor which initially finds those genes which need to be transcribed. (T/F)
8. DNA polymerase requires a free 3’ hydroxyl group on the end of a nucleotide chain to serve
as the attachment point for the next nucleotide. When replication is started, therefore, a short
__ primer must be synthesized first.
a. polypeptide
b. RNA
c. McGuffey d. hydrophobic
9. Because part of the DNA strand in synthesized in pieces (Okazaki fragments), the enzyme __
is necessary to attach the pieces together.
a. DNA polymerase III b. DNA polymerase I
c. Okazakase d. DNA ligase
10. The DNA of a certain organism has guanine as 30 percent of its bases. What percentage of
its bases would be adenine?
a. 10
b. 20 c. 30
d. 40
e. 50
11. Which of the following statements about DNA structure and replication in prokaryotes and
cell organelles is correct?
a. there is a single circular chromosome composed of DNA
b. chromosomes are wound around nucleosome cores
c. replication begins at multiple origins
d. chromosomes line up in the center of the cell during replication
MOLECULAR GENETICS
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12. Chemicals commonly induce mutations by
a. causing chromosomal breaks.
b. reversing the nucleotide sequence in enhancer regions
c. attaching to nitrogenous bases and interfering with their normal H bonding patterns
d. energizing thymidines to form dimers, interfering with their normal H bonding
patterns
13. Ultraviolet light induces mutations by
a. causing chromosomal breaks.
b. reversing the nucleotide sequence in enhancer regions
c. activating nitrogenous bases and interfering with their normal H bonding patterns
d. energizing thymidines to form dimers, interfering with their normal H bonding
patterns
14. As part of a nucleosome, you would expect to find
a. DNA
b. histone proteins c. RNA
d. a and b
e. a, b and c
Short Answer
1. On the diagram below of an opened DNA molecule, sketch in the leading strand of DNA
replication, the lagging strand of DNA replication, RNA primers and Okazaki fragments.
Indicate where continuous synthesis and discontinuous synthesis are occuring. What is the
purpose of the RNA primers?