Question

Helllo! I am stuck on this question (it is the second part of a question, but I was able to get the answer to the first part!).

A particular gene codes for a mature mRNA transcript that contains 900 bases, which is translated into a protein containing 200 amino acids.

1. Another mutant form of the gene yields a 1200-base mature mRNA transcript and the protein made from the mutant gene contains 150 amino acids and has no enzymatic activity. What mutation may have occurred that would lead to a longer mature mRNA transcript and a modified coding region? Explain why the activity of this protein might be a complete loss of function.

Answer 1

Most possibly there is frame shift point mutation which modified a splicing site (splice site mutation) and non-sense mutation.

A point mutation that occured at the boundary of an exon and an intron. This mutation disrupted RNA splicing resulted in the inclusion of introns and hence the size of mRNA increased from 900 to 1200.

Same mutation caused nonsense mutation in the sequence that resulted in a premature stop codon. Therefore, amino acid chain reduced from 200 to 150.