Question

Following (A,B,C and D) are four closely related species, having similar amino acid sequences in their haemoglobin chain. If amino acid substitution occurs in the chain of haemoglobin in an order given in table, then their evolutionary pattern can be depicted by

Comparison of species	Number of amino acid substitution
A and B	10
B and C	30
A and C	20
D and C	27
A and D	20
D and B	1

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

Although it is a hypothetical situation, amino acid substitution includes substitution of one or more amino acids in place of others. A polypeptide chain can significantly alter the physiological properties of the genetic code or amino acid properties.
The polypeptide that has the least substitution in its amino acid sequence will be more stable in the race of evolution. In the table given, species B and D have the least substitution in their amino acid sequence hence in the long run of evolution, the polypeptide chain in these two species would be more closely related . Species B and C have the highest amino acid substitution which can lead to more changes in the parent polypeptide and this would lead to more distance or evolutionary gap among species.