Question 27 (1 point) A trait known as Xeroderma Pigmentosum (XP) is Question 27

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Question 27 (1 point)

A trait known as Xeroderma Pigmentosum (XP) is

Question 27 options:

A human desease characterized by reduced production of melanin, which is a skin pigment

A human disease that can be caused by mutations in the nucleotide excision repair (NER) system

An autosomal recessive trait caused by mutations in the Photolyase gene

A bacterial phenotype caused by mutations in the Photolyase gene

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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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Question 37 (1 point)

In gel electrophoresis, which of the following DNA fragments would travel the farthest distance from the sample well?

Question 37 options:

ATCCCGAT

ATCCCG

ATCC

AT

ATCCCGATTGCACGTT

A human desease characterized by reduced production of melanin, which is a skin pigment

A human disease that can be caused by mutations in the nucleotide excision repair (NER) system

An autosomal recessive trait caused by mutations in the Photolyase gene

A bacterial phenotype caused by mutations in the Photolyase gene

Explanation / Answer

27.Correct answer is:.A human disease that can be caused by mutations in the nucleotide excision repair (NER) system.

Reason:Mutations that lead to defects on enzymes of NER repair system of DNA causes Xeroderma pigmentosum.

28.Correct answer is:Another DNA polymerase

Reason:Other DNA polynerases are involved in SOS repair.

29.Correct answer is:True

30.Correct answer is:True

31.Correct answer is: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)

32.Correct answer is:Genes responsbile for DNA repair

Reason: DNA repair if not corrected lead to unfunctional/malfunctional proteins that cause diseases.

33.Correct answer is:cut the DNA at defined sequences.

Reason:The defined sequemces at which restriction endonuclease cuts is known as restriction site.

34.Correct answer is:5'-GGATCC-3'

Reason: 5'-GGATCC-3'

3'-CCTAGG-5'

35.Correct answer is:DNA ligase

Reason:DNA ligase helps to seal vector and DNA together.

36.Correct asnwer is : 4

Reason:Since there are 4 restriction sites, cut would be made at 4 sites resulting in 4 ds DNA.

37.Correct answer is: AT

Reason: Small size fragments would travel faster in a gel than large sized fragments.

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