task A. Figure A shows a sample of an mRNA containing two exons (boxes), exon 2
ID: 268851 • Letter: T
Question
task
A. Figure A shows a sample of an mRNA containing two exons (boxes), exon 2 and exon 3, which is separated by an intron (line). A mutation (marked with an X) causes the introduction of a new 5 'splice site above the normal 5' splice site.
Outlines the mRNA that results after the processing of mRNA A. What changes do you expect in the amino acid sequence of the protein encoded by the mutated mRNA?
B. Figure B shows how a mutation in intron 2, which connects exon 2 with exon 3, causing the formation of a new 5 'splice site. This also causes the activation of one "Cryptic" 3 'splice site upstream compared to the new 5' splice site. X shows the location of the mutation and the new 5 'splice site. The cryptic 3 'splice site is also marked. "Cryptic" means that the splice site contains the required consensus sequences, but usually not used for splicing.
Outlines the mRNA that results after the processing of mRNA B. How does it differ Any amino acid changes in the encoded protein resemble those that occurred in A?
5' Exon 2 Exon 3 3' 5' Exon 2 Exon 3Explanation / Answer
A. Since exon A has a new splice site, the exon 1 will either get truncated and a shorter form of exon 1 will be formed. If exon 2 and exon 3 joins togetherafter 5' and 3' splicing, then the protein/polypeptide that gets translated will be either shorter compared to normal splicing mechanism without mutation or some part of intron will also be present in the polypeptide (hence longer). Thus the protein may or may not be fully functional after translation and folding. Since mutation is there , it may lead to change in coding sequence , hence corresponding amino acid will be changed or a stop codon may be introduced that leads to premature translation of mRNA Exon A.
B. 3' and 5' splice site will lead to splicing but some part of intron will be present along with the exon3. Thus depending upon the length of exon 3 and intron remaining, coding sequence will be altered and hence polypeptide translated may or may not be a functional one. Compared to question A , defintiely the sequence in both cases will be different.
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