Study the following carefully and explain why mutation (A) did not cause any sickle cell anemia in spite of change in the molecular structure of the gene which codes for Haemoglobin, when as a similar mutation (B) did. (The question is based on properties of the genetic code. c= codon, a = amino acid, Hb = Haemoglobin)
Codons for Hb:`C_1 - C_2 -C_3 -C_4 - C_5` -G AA -GAA-`C_8`...
Amino acids in Hb : `a_1-a_2-a_3-a_4-a_5`- Glutamic acid- Glutamic acid -`a_8`...... (Normal Haemoglobin )
Mutation (A) : `C_1 -C_2 - C_3 -C_4 -C_5-GAG-"GAA"-C_8...... a_1-a_2 - a_3-a_4-a_5`-Glutamic acid -Glutamic acid -`a_8`.... (Normal Haemoglobin )
Mutation (B) : `C_1 -C_2 - C_3 -C_4 -C_5-GAG-"GAA"-C_8...... a_1-a_2 - a_3-a_4-a_5`-Valine-Glutamic acid -`a_8`.... (Sickle cell Haemoglobin )

Explanation

Genetic code degenerate le more than one code for one amino acid
- Both GAG GAA code for glutamic acid.
- Mutation of third base/nucleotide - to change in phenotype in mutation A/Wobble hypothesis
In case of change on 2nd codon of triplet code as in Mutation B. codon stands for a different amino acid valine
Hb becomes different normal Hb becomes Hbs / Structure of protein charged