Question

A protein with a wild-type allele (P^wt) and protein with a mutant allele (P^m) are one amino acid in the position 12 of the protein chain. The mutant allele's sequence is 5'CTT whereras the wild-type allele's sequence is 5'CAT.

Using an amino acid chart, find :

P^wt in position #12

P^m in position #12

Answer 1

Answer: P^wt in position #12 = Histidine

               P^m in position #12 = Luecine

Explanation: The sequence mentioned here is the DNA sequence and it is in 5’to 3’ direction.

Hence first find out the complementary DNA strand sequence which will be in 3’to 5’ direction as this strand of DNA known as the anti-sense strand serves as the template for mRNA synthesis which will be in 5’to 3’ direction.

Then from the mRNA sequence, with the help of genetic code table the wild type as well as the mutated amino acid can be found out.

Wild type DNA 5'CAT

Hence its complementary DNA strand sequence will be 3’GTA

And the mRNA strand synthesized on the above sequence will be 5’CAU

Hence the amino acid at the 12^th position of the wild type protein P^wt is Histidine.

Mutant DNA sequence is 5'CTT

Hence its complementary DNA strand sequence will be 3’GAA

And the mRNA strand synthesized on the above sequence will be 5’CUU

Hence the amino acid at the 12^th position of the wild type protein P^m is Luecine.

Note: complementary base pairing in DNA is Adenine with thymine and vice versa and guanine (G) with cytosine (C) and vice versa.

In case of RNA pairing of guanine(G) is with cytosine (C) and vice versa. Thymine on DNA will pair with adenine in RNA but adenine (A) on DNA is paired with Uracil (U), as instead of thymine RNA has Uracil.