question_answer

What base is responsible for hot spots in spontaneous point mutation?

A)  Adenine                                             

B)  Guanine

C)  5- bromouracil                 

D)  5- methylcytocine

Correct Answer: C

Solution :

                 Point mutations are changes in the hereditary message of an organism. They may result from physical or chemical damage to the DNA or from spontaneous error during DNA replication, eg, alteration during replication of nucleic acid in incorporation of base analogous like 5 Bromo uracil (Bu) or 5-Bromodeoxy uredine (Budi). 5 Bu can pair with adeninejust like thymine. Occasionally 5 Bu loses a hydrogen atom in position 1 and pair with guanine instead of adenine. The higher frequency of pairing mistake are due to higher electronegativity of Br in Bu as compared to methyl group in thymine (methyl uracil).                 Base pairing between adenine and normal keto state of 5 Bu.                 Base pairing between guanine and 5 Bu.