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12th Biology 2012 Set1 Delhi Board Paper Solution

Question 25

Given below is the representation of amino acid composition not the relevant translated portion of -chain of haemoglobin, related to the shape of human red blood cells.


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

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



(b)   In a sufferer, the codon GAG is replaced by GUG in the mRNA. Hence, during translation of the defective mRNA, Glutamic acid is replaced by Valine.

(c) The disease represented by the defect in the given gene is sickle-cell anaemia. It is an autosomal recessive trait. This disease is transmitted to the progeny when both the parents are carriers for the disease (heterozygous).