Principle of Inheritance and VariationMediumBloom L3
Question
In sickle-cell anaemia glutamic acid is replaced by valine. Which one of the following triplet codes for valine?
Options
A.G G G
B.AAG
C.GAA
D.GUG
Solution
Sol.(d) [Key Concept: Sickle Cell Anaemia — Valine Codon] Valine is coded by the triplet GUG (in mRNA). In sickle cell anaemia, the 6th codon of the beta-globin mRNA changes from GAG (glutamic acid) to GUG (valine) due to a single base pair substitution (A→T in DNA, A→U in mRNA). GGG codes for glycine; AAG codes for lysine; GAA codes for glutamic acid (the normal amino acid). Only GUG codes for valine — the amino acid responsible for the sickling of RBCs.
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