Question

Which of the mutagen causes frameshift mutation?
A. 2-aminopurine
B. Proflavine
C. 5-bromouracil
D. Methanesulfonates

Answer 1

Hint:Protein structure is altered by three types of mutations
1. Gene or point mutations involve the addition, deletion, or replacement of a base pair in a gene.
2. Addition or deletion of DNA chunks during crossing over (recombination) between DNA strands under special conditions; and
3. Jumping genes which shuffle their location from one chromosome to another due to the similarity of DNA sequences flanking them.

Complete answer:All the mutations are reflected in the proteins. This is because the mRNA transcribed from the mutated gene will lack a segment or a base, or will have an additional or altered segment or base.
The abnormal mRNA will introduce different amino acids in the polypeptide synthesized with its altered message.
If a single base is altered in the gene, only one codon in mRNA will change and this will change a single amino acid in the polypeptide.
If the number of bases inserted in or deleted from a gene is not divisible by 3, all the base triplets(codons) beyond the site of mutation are altered in the mRNA transcribed from it. This will result in the formation of entirely a new polypeptide. This is called a frameshift mutation.
Proflavin is an acridine dye that intercalates itself between base pairs of the DNA chain thereby causing loss or gain of a single nucleotide.
The gene mutation alters the base sequence of the whole genetic frame from the point of mutation called frameshift mutation.

So the correct answer is option is B. Proflavin.

Note:2-aminopurine causes transition mutation which is purine analogue, 5-bromouracil causes transition and is a pyrimidine analogue acts as thymine in DNA replication and methane sulphonate causes mutation by base substitution