Question 28 (1 point) Under conditions of extreme DNA damage, prokaryotes will u

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Question 28 (1 point)

Under conditions of extreme DNA damage, prokaryotes will use which of the following DNA polymerases to replicate damaged DNA?

Question 28 options:

DNA Pol I

DNA Pol III

Another DNA polymerase

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Question 29 (1 point)

Translesion DNA synthesis is performed by a specialized class of DNA polymerases (low-fidelity DNA polymerases) that can deliberately ignore the standard base-pairing rules, which is in stark contrast to regular DNA polymerases.

Question 29 options:

True

False

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Question 30 (1 point)

One negative side-effect of using low-fidelity DNA polymerases for DNA synthesis is that they make DNA replication mistakes even when using a perfectly normal DNA template strand, causing unnecessary mutations. Therefore, cells activate such DNA polymerases only in situations of extreme DNA damage, such as during the bacterial SOS response.

Question 30 options:

True

False

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Question 31 (1 point)

DNA mutations can be caused by mistakes during DNA replication. Suppose that during replication of a perfectly normal DNA template strand, a regular high-fidelity DNA polymerase makes a mistake by inserting G opposite T, and this mistake goes unnoticed by DNA polymerase’s proofreading activity. After the fact, what is one way in which the cell might still know whether this GT mismatch should be an AT pair or a GC pair?

Question 31 options:

The cell has no way of telling which pair it should be; it simply assumes that each GT mismatch should be corrected by mutating G to A to make it an AT pair

The cell has no way of telling which pair it should be; it simply assumes that each GT mismatch should be corrected by mutating T to C to make it a GC pair

The cell methylates some adenines in the old DNA template strand to distinguish it from the newly synthesized DNA strand; the cell will conclude that the correct base is on the methylated strand (T)

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Question 32 (1 point)

Mutations in which genes would be most detrimental to an organism?

Question 32 options:

Genes responsbile for DNA repair

Genes responsbile for melanin production

Genes responsible for fingernail growth

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Question 33 (1 point)

Restriction endonucleases:

Question 33 options:

prevent the entry of DNA into bacteria.

can only be used on DNA from certain organisms.

remove individual bases from the ends of a DNA sequence.

cut the DNA at defined sequences.

cut the DNA at random sequences.

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Question 34 (1 point)

Which of the following is a palindromic sequence recognized by a restriction endonuclease (only one strand is shown)?

Question 34 options:

5'-GGATCC-3'

5'-CCTGAA-3'

5'-ATGGTA-3'

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Question 35 (1 point)

Which enzyme is required to insert DNA into a cloning vector?

Question 35 options:

DNA polymerase

DNA gyrase

DNA ligase

DNA helicase

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Question 36 (1 point)

A circular double stranded plasmid pABC123 contains four EcoRI restriction sites. How many double stranded DNA fragments will result from cutting this plasmid with EcoRI?

Question 36 options:

1

4

5

8

10

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DNA Pol I

DNA Pol III

Another DNA polymerase

Explanation / Answer

28). b). DNA Pol III

DNA polymerase III: It is involved in prokaryotic replication and it also has proofreading capabilities. It can correct the mistakes identified during proofreading by means of exonuclease activity and it moves in 3’ to 5’ direction. DNA polymerase is a component of replisome, so it is involved in DNA replication. The rate of base pair synthesis by DNA polymerase III is approximately 1000 nucleotides per sec. The activity of DNA polymerase III starts after the separation of double helical strand at the origin of replication.

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