A Gene involved in DNA replication has been inactivated by a mutation in a cell.

Question

A Gene involved in DNA replication has been inactivated by a mutation in a cell. In the abscence of this protien the cell attempts to replicate its DNA. What would happen if the mutated gene encoded the sliding clamp loader ?

A. Too mant DNA polymearse would try to replcate DNA

B. The DNA polymearse would synthesize a short DNA chain of a few cnucleotides only and then fall off the template

C. Excessive number of strands of DNA would be replicated

D. The replication forks would not know which direction to move

E. THe leading strand of new DNA would be made, but the lagging strand would not be made

Explanation / Answer

A DNA clamp is also known as sliding clamp. It is a protein fold that serves as a processivity-promoting factor in DNA replication. It is a critical component of the DNA polymerase III holoenzyme, the clamp protein binds DNA polymerase and prevents its dissociation from the template DNA strand. The clamp-polymerase protein–protein interactions are stronger and more specific and the presence of the sliding clamp dramatically increases the number of nucleotides that the polymerase can add to the growing strand per association event. The presence of the DNA clamp can increase the rate of DNA synthesis up to 1,000-fold compared with a nonprocessive polymerase.

If the mutated gene encoded the sliding clamp loader, the DNA polymearse would synthesize a short DNA chain of a few nucleotides only and then fall off the template. this is because mutation in the gene may affect its efficiency of binding the DNA polymerase with template strand. Option B is correct.

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