Question

Given below is the representation of amino acid composition not the relevant translated portion of $\beta$-chain of haemoglobin, related to the shape of human red blood cells.
(a) Is this representation indicating a normal human or a sufferer from certain related genetic disease? Give reason in support of your answer.
(b) What difference would be noticed in the phenotype of the normal and the sufferer related to this gene?
(c) Who are likely to suffer more from the defect related to the gene represented the males, the females or both males and females equally? And why?

Answer 1

(a) This representation is of a normal person. In a normal person, the mRNA possesses the codon GAG which codes for the glutamic acid.

(b) In the sufferer, the GAG is replaced by GUG in the mRNA which codes for valine. So, glutamic acid is replaced by valine during translation due to which RBC would be sickle-shaped.

(c) The disease is sickle cell anemia which is an autosomal recessive trait. Affected male in an autosomal recessive trait has to be homozygous recessive for defected allele i.e.HbS/HbS. Since both alleles are defected he can only transmit defected alleles to his children be it daughter or son. That is why both males and females will be equally affected.