Question

A) Which property of DNA replication enables accurate mismatch repair to prevent mutation?

a) Adenine methylase lags behind the DNA polymerase

b) the proofreading ability of DNA polymerase

c) the error-free nature of DNA pol. III

d) the sister chromatid can be used as a template

B) which DNA repair mechanism uses the sister chromatid as a template for repair?

a) nucleotide excision repair

b) double-stranded break repair

c) postreplication repair

d) base excision repair

C) indicate which substitutions require one or more than one mutation

Val to ala

Leu to Gly

His to glu

Answer 1

Ans-A- DNA polymerase has 3' to 5' exonuclease activity which repairs the mismatch when ever any wrong nucleotide is added by mistake. Option B is correct.

Ans-B- sister chromtids are used as a template when both the strand of DNA are damage. So the information needed to repair the DNA strand is taken from sister chromtids. Option B is correct.

Ans-C- if we want to substitute one amino acid from other amino acid minimum one substitution is required in DNA bases. Val to ala substitution require only one mutation while Leu to gly and His to glu requires two mutation. Hence all requires minimum one mutation.