A eukaryotic proteinencoding gene contains two introns and t

A eukaryotic protein-encoding gene contains two introns and three exons: exon 1-intron 1-exon 2-intron 2-exon 3. The 5\' splice site at the boundary between exon 2 and intron 2 has been eliminated by a small deletion in the gene. Describe how the pre-mRNA encoded by this mutant gene would be spliced. Indicate which introns and exons would be found in the mature mRNA of this mutant. The open reading frame (ORF) begins with _____ and ends with _____ codon

Solution

1. exon1-intron1-exon2-intron2-exon3. if the 5\'site of splicing boundry between exon 2 and intron 2 has been eliminated then the splicing at  intron 2 will not occur because 5\' splice site is important for neucleophilic attack by the 3\'OH of the exogenous G nucleotide. therefore after splicing the preMRNA sequence will be exon1-exon2-intron2-exon3.

2. open reading frame starts with AUG (met) and ends with UAG , UAA , UGA