Question 22 (1 point) Treating cells with an intercalating agent can induce whic

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Question 22 (1 point)

Treating cells with an intercalating agent can induce which type of DNA mutation?

Question 22 options:

Missense mutation

Silent mutation

Neutral mutation

Frameshift mutation

Nonsense mutation

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Question 23 (1 point)

It is often said that the “proofreading” activity of DNA polymerases that replicate the majority of cellular DNA (such as bacterial DNA polymerase III) represents the “first line” of defense against mutations. What exactly does it mean?

Question 23 options:

If DNA polymerase III makes a mistake during making a new DNA strand, it will quickly realize its mistake, go back to delete the wrong nucleotide, replace it with the correct nucleotide, and only then continue synthesizing the rest of the DNA strand

When all DNA replication is complete, DNA polymerase III will be the first protein to float around looking for replication mistakes; when it notices such a mistake, DNA polymerase III will bind DNA and correct the mistake

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Question 24 (1 point)

Exposure to high-energy UV light photons can cause a lot of DNA damage. One mechanism of such damage is creation of so-called pyrimidine dimers. Which of the following would be an example of such a pyrimidine dimer?

Question 24 options:

Two consecutive T bases on the same DNA strand with direct covalent bonds between them

Two T bases on the opposite DNA strands that form an abnormal base pair linked through four hydrogen bonds

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Question 25 (1 point)

Photolyase is an enzyme that can break up UV-induced TT dimers. This process is called “light repair” because

Question 25 options:

TT dimers are formed during exposure to light

Photolyase is activated by light

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Question 26 (1 point)

Nucleotide excision repair (NER) is known as the “dark repair” mechanism. This is because

Question 26 options:

This mechanism requires dark conditions for its activation

This mechanism does not require light for its activation

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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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Missense mutation

Silent mutation

Neutral mutation

Frameshift mutation

Nonsense mutation

Explanation / Answer

22.Ans.Frameshift mutations

intercalating agents are the mutagens which binds between two bases of DNA strands. they have the size that exactly fits in between the two bases of DNA. upon binding these agents changes the reading frame which effects the or which changes the final Protein.this kind of mutation called Framshift mutation which effects the final Protein outcome.

23.Ans.If DNA polymerase III makes a mistake during making a new DNA strand, it will quickly realize its mistake, go back to delete the wrong nucleotide, replace it with the correct nucleotide, and only then continue synthesizing the rest of the DNA strand

The Proof reading activity of DNA Pol.III functions in reducing the error rate of replication. while replication process if mismatch base is introduced into the strand DNA polymerase halts further elongation process, and activates its proof reading activity. the first step it moves form 3'-5' direction and remove the mismatched base along with the mismatched base it excise some more bases once it remove mismatched base again activates the polymerization process and synthesize new DNA strand.

24.Ans.Two consecutive T bases on the same DNA strand with direct covalent bonds between them

if DNA exposed to UV radiation for long time the Pyrimidine bases for example the Thymine bases present in the same strand of the DNA forms dimes known as Thymine dimers. these dimers are not replicated by DNA polymerase, these dimers inhibit the polymerase and arrest the replication process.

25.Ans.Photolyase is activated by light

Photolyase are DNA repair enzymes involves Photoreactivation process. these involves in removal of pyrimidine dimers for example thymidine dimers those are produced due to the exposure of DNA to UV light. these enzymes absorbs energy from UV region activates and promote catalysis

26.Ans.This mechanism does not require light for its activation

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