You are studying a mutation of a signaling protein. The mutant protein is comple

Question

You are studying a mutation of a signaling protein. The mutant protein is completely nonfunctional and is shorter than wild type. The mutant mRNA, however, is significantly longer than wild-type mRNA. You find the mutation is a single base-pair substitution. This substitution is not in the coding sequence but is the second base pair in the first intron. Propose a molecular explanation for how a single base change in the intron results in a longer mRNA and a shorter non-functional protein product.

Explanation / Answer

exon and intron junction are demarketed with specific sequences, mostly enriched by AG-GT sequences. all the exon intron junctions must not be these sequences,as there are reported as many as 9 cryptic site for exon inron junctions. there are specific exon junction complexes (EJC) which is a specific machinary to act on exon intron junction. they have important roles in splicing and translation. so if there is single nucleotide change at the 2nd base pare of the intron, it might have great effect to abolish the exon intron junction. this may lead to loss of recognization of EJC for that site to be spliced, which may result in making that into the after proper exon sequence and finally into the m-RNA unspliced which is ready for translation. these events will produce all the amonoacids in that intron into the protein, making that a non-functional protein.

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