The following sequence is the nucleotide sequence encoding a wild type allele fo

Question

The following sequence is the nucleotide sequence encoding a wild type allele for a particular gene. The sequence begins with a start codon and ends with a stop codon. 5' ATGCCGCACGAAGTATAA 3' a. What is the amino acid sequence encoded by this nucleotide sequence? b. Within this sequence, two different mutations have been identified in the population. For each mutation, identify whether it is a transition, transversion or deletion/insertion. In addition, indicate whether the mutation is a silent, missense, nonsense or frameshift mutation. Mutation 1: 5' ATGCCGCACTAAGTATAA3' Mutation 2: 5' ATGCCGGCACGAAGTATAA 3'

Explanation / Answer

a. The amino acid sequence will be: met-pro-his-glu-val (Here first codon is ATG which is start codon and codes for methionine and the last codon TAA is stop codon and does not code for any amino acid. Rest all amino acids are according to their codon)

b. Mutation 1. ATGCCGCACTAAGTATAA. Here 10th nucleotide G of original sequence is converted into T. Guanine is purine and thymine is pyrimidine. Hence this mutation is transversion. (transversions are interchanges of purines for pyrimidine bases). This is the case of nonsense mutation because here GAA which dodes for glutamine has been converted into TAA whch act as terminating codon or stop codon. (nonsense mutation is defined as changing of a sense codon into terminating codon)

Mutation 2. ATGCCGGCACTAAGTATAA. Here an extra nucleotide (G) after 6th nucleotide (G) has been inserted. Hence this is insertion mutation. This is the case of frameshift mutation because whole reading frame has been changed due to insertion of an extra nucleotide because of triplet nature of codon.

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