You obtain the sequence of a gene containing 10 exons, 9 introns, and a 3' UTR containing a polyadenylation consensus sequence. The fifth intron also contains a polyadenylation site. To test whether both polyadenylation sites are used, you isolate mRNA and find a longer transcript from muscle tissue and a shorter transcript from all other tissues. Which of the following is the most likely mechanism underlying these alternative transcripts?
A. The mRNA in muscle cells is edited to eliminate the polyadenylation sequence in exon 5
B. An alternative CPSF protein is expressed in muscle cells with lower affinity for the polyadenylation sequence in exon 5.
C. The fifth exon is spliced out of the mature mRNA transcript in muscle cells
D. Muscle cells have less effective polyadenylation than other tissues
You obtain the sequence of a gene containing 10 exons, 9 introns, and a 3' UTR containing a polyadenylation consensus sequence. The fifth intron also contains a polyadenylation site. To test whether both polyadenylation sites are used, you isolate mRNA and find a longer transcript from muscle tissue and a shorter transcript from all other tissues. Which of the following is the most likely mechanism underlying these alternative transcripts?
A. The mRNA in muscle cells is edited to eliminate the polyadenylation sequence in exon 5
B. An alternative CPSF protein is expressed in muscle cells with lower affinity for the polyadenylation sequence in exon 5.
C. The fifth exon is spliced out of the mature mRNA transcript in muscle cells
D. Muscle cells have less effective polyadenylation than other tissues
