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Due to a mutation in gene A, amino acid ‘Glu’ in position 15 of enzyme A (the wi

ID: 215664 • Letter: D

Question

Due to a mutation in gene A, amino acid ‘Glu’ in position 15 of enzyme A (the wild polypeptide) is replaced by ‘Ala’. Individuals who are heterozygous for the mutant allele (Aa) don’t have any phenotypic alterations. Based on this observation, which of the following is correct about this mutation?

The mutation has occurred in the promoter.

The mutation has occurred in the last intron of the gene.

The mutation is a base insertion in the second exon.

The mutation is recessive.

The mutation is a neutral dominant mutation.

Two of the above are correct

The start codon:

binds to anticodon 3'CAT5' on the initiator tRNA

is capable of binding to several tRNAs

is located at the 5' end of mRNA where the ribosome attaches to the 5' cap

specifies various amino acids in bacteria.

is closer than other codons to the 5' end of the mRNA

A.

The mutation has occurred in the promoter.

B.

The mutation has occurred in the last intron of the gene.

C.

The mutation is a base insertion in the second exon.

D.

The mutation is recessive.

E.

The mutation is a neutral dominant mutation.

F.

Two of the above are correct

Explanation / Answer

Due to a mutation in gene A, amino acid ‘Glu’ in position 15 of enzyme A (the wild polypeptide) is replaced by ‘Ala’. Individuals who are heterozygous for the mutant allele (Aa) don’t have any phenotypic alterations. Based on this observation, which of the following is correct about this mutation. The option F is correct i.e. two options are correct.

The mutation has occurred in the last intron of the gene or the mutation is recessive. The option A, C and E are incorrect because if the mutation is to occur in the promotor or is a base insertion in the second exon or is a neutral dominant mutation, then it will surely show its affect.

The start codon the option C is correct i.e. is located at the 5' end of mRNA where the ribosome attaches to the 5' cap.As start codon is AUG and it will bind to that tRNA only which carry methionine or formyl methionine in bacteria.Translation starts from 5 ' end where start codon AUG is present and proceeds towards 3' and terminate when stop codon (UAA,UAG,UGA) are readed by ribosome.

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