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UNCC BIOL3111 Exam 3 Chapter 6 Study Questions and Answers
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UNCC BIOL3111 Exam 3 Chapter 6 Study Questions and Answers
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UNCC BIOL3111 Exam 3 Chapter 6 StudyQuestions and Answers
A mismatched base pair causes ____________ in the DNA backbone. If this were the
only indication of an error in replication, the overall _____________________ would be
much higher.
This is because __________ alone does not tell the mismatch repair system
_________________________________________________________________. -
ANS-distortion, rate of mutation.
distortion,
which base is incorrect and which was originally part of the chromosome.
A pregnant mouse is exposed to high levels of a chemical. many of the mice in her little
are deformed, but when they are interbred with each other, all their offspring are normal.
Which TWO of the following statements could explain these results?
(a) In the deformed mice, somatic cells but not germ cells were mutated.
(b) The original mouse's germ cells were mutated.
(c) In the deformed mice, germ cells but not somatic cells were mutated.
(d) The toxic chemical affects development but is not mutagenic. - ANS-A- In the
deformed mice, somatic cells but not germ cells were mutated.
D- The toxic chemical affects development but is not mutagenic.
Affected individuals in some families with a history of early-onset colon cancer have
been found to carry mutations in ____________________. Mutations arising in
_____________________ are not inherited. A defect in DNA synthesis or nucleotide
biosynthesis would probably _______________. - ANS-mismatch repair genes,
somatic cells,
be lethal.
Beside the distortion in the DNA backbone caused by a mismatched base pair, what
additional mark is there on eukaryotic DNA to indicate which strand needs to be
repaired?
(a) a nick in the template strand
(b) a chemical modification of the new strand
(c) a nick in the new strand
(d) a sequence gap in the new strand - ANS-C- A nick in the new strand
During DNA replication in a bacterium, a C is accidentally incorporated instead of an A
into one newly synthesized DNA strand. Imagine the error was not corrected and that it
has no effect on the ability of the progeny to grow and reproduce.
A- After this original bacterium has divided once, what proportion of its progeny would
you expect to contain the mutation?
, B- What proportion after three more rounds of DNA replication and cell division? - ANS-
A- 1/2, 50%
B- 1/4, 25%
Even through DNA polymerase has a proofreading function, it still introduces errors in
the newly synthesized strand at a rate of 1 per 10^7 nucleotides.
To what degree does the mismatch repair system decrease the error rate arising from
DNA replication?
(a) 2-fold
(b) 5-fold
(c) 10-fold
(d) 100-fold - ANS-D- 100-fold
Homologous recombination is an important mechanism in which organisms use a
"backup" copy of the DNA as a template to fix
____________________________________ without loss of genetic information.
Which of the following is NOT necessary for homologous recombination to occur?
(a) 3′ DNA strand overhangs
(b) 5′ DNA strand overhangs
(c) a long stretch of sequence similarity
(d) nucleases - ANS-double-strand breaks,
B- 5' DNA stand overhangs
Human beings with the inherited disease xeroderma pigmentosum have serious
problems with lesions on their skin and often develop skin cancer with repeated
exposure to sunlight.
What type of DNA damage is not being recognized by the cells of these individuals?
(a) chemical damage
(b) X-ray irradiation damage
(c) mismatched bases
(d) ultraviolet irradiation damage - ANS-D- ultraviolet irradiation damage
In addition to the repair of DNA ____________________________, homologous
recombination is a mechanism for generating genetic diversity by swapping segments of
parental chromosomes.
During which process does swapping occur?
(a) DNA replication
(b) DNA repair
(c) meiosis
(d) transposition - ANS-double-strand breaks,
C- meiosis
In somatic cells, if a base is mismatched in one new daughter strand during DNA
replication, and is not repaired, what fraction of the DNA duplexes will have a
permanent change in the DNA sequence after the second round of DNA replication?
(a) 1/2
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