Question

In: Biology

In the mismatch repair system, the MutS protein initiates the repair process, and the MutHL excision...

In the mismatch repair system, the MutS protein initiates the repair process, and the MutHL excision complex acts by cutting

A)

The methylated strand of the double helix

B)

Any U:A base pairs found in the DNA

C)

Any G:T base pair

D)

The non-methylated strand of the double helix

E)

The site of the helix distortion

Solutions

Expert Solution

Answer- D) The non-methylated strand of the double helix

Explanation- In prokaryotes, mismatch repair system removes misincorporated bases in daughter strand. This system recognizes daughter strand on the basis of methylation pattern. Parent DNA strand is methylated and newly synthesized strand is not methylated just after synthesis of new strand so that mismatch repair system works before methylation of new DNA strand. So that, this repair mechanism works after DNA synthesis and before methylation of daughter strand. In this, MutS protein recognizes mismatch base in daughter strand, then MutH binds the complex and activated by MutL. Then MutH nicks the daughter DNA and then UvrD is recruited at the site which separates parent and daughter DNA strand. Then exonuclease cleave daughter DNA and then new correct nucleotides are added by DNA polymerase III and gap is sealed by DNA ligase. So that the MutHL excision complex acts by cutting the non-methylated strand of the double helix.


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