In: Biology
A mouse carries a mutation in somatic cell that changes a lysine codons into a glutamic acid codon. Prior to this mutation the mouse was exposed to X-Ray, UV light, Proflavin, 5-bromouracil and EMS. Which of these agents would be the most likely the cause of the mutation?
A. Proflavin
B. EMS
C. UV light
D. 5-bromouracil
Lysine is coded by AAG or AAA codon. Glutamic acid can be coded by GAA or GAG codons. Hence, a change from A to G in first nucleotide of the codon is observed.
Ethyl methane sulfonate or EMS induces spontaneous mutation in DNA, which are mostly point mutations. EMS produces both GC to AT and AT to GC transition mutations, it is the most likely source of lysine to glutamic acid mutation observed.
The 5- bromouracil mimics the thymine base and can base pair with guanine to cause from TA to CG. However, there is only change in one nucleotide, 5’ bromouracil would have changed tow nucleotide as 3’TTA5’ would be replaced by 3’BrU BrU A5’ or even three changes (in AAA).
Proflavin is a mutagen that can intercalate between DNA strands. It mostly induces frameshift mutations. UV light induces formation of pyrimidine dimers (thymine dimers). There is no thymine base involved in the lysine codon.
Right choice: B. EMS.