A gene involved in DNA replication has been inactvated by mutation in a cell. In

Question

A gene involved in DNA replication has been inactvated by mutation in a cell. In the absence of this gene portien product, the cell attempts to replicate its DNA. What would happen if the mutated gene encoded the helicase involved in DNA replication ?

A. DNA would supercoil rapidly

B. Little or no DNA will be synthesized

C. The leading strands of new DNA would be made, but the laggin strand would not be made

D. The polymerase would synthesize a short DNA chain of a few nucleotides only then fall off the template.

E. A and D

Explanation / Answer

Ans: E. A and D

A. DNA would supercoil rapidly

D. The polymerase would synthesize a short DNA chain of a few nucleotides only then fall off the template.

Reason:

Helicase is responsible for ‘unzip’ the double helix structure of the DNA molecule in DNA replication. This breaks the hydrogen bonds holding the complementary. If the mutated gene encoded the Helicase involved in DNA replication DNA would supercoil rapidly and the polymerase would synthesize a short DNA chain of a few nucleotides only then fall off the template.

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