In Tay Sachs Disease, a change in a base pair knocks out the protein function. The protein made is shorter, while each mutant mRNA is 30% longer than normal mRNA. A deletion of a base pair causes this situation.
I am wondering how a deletion in the frame shift can cause transcription resulting in longer mRNA and then leading to a shorter protein during translation. I know that an deletion can result in a premature stop codon, but shouldn’t the termination area of the template DNA still be largely unaffected? Can anybody explain?
I don’t know if this is the case in Tay-Sachs, but here is one way a point mutation could result in both a shorter protein and a longer mRNA. If the mutation occurs at a splice junction or a splice-regulatory site, the removal of an intron may be deactivated. In that case, the intron appears in the mRNA, increasing its length. An in-frame stop codon in the intron may result in translation of a shorter polypeptide.
