In brain cells, a protein is present that specificakly binds to the 3\' splice s

Question

In brain cells, a protein is present that specificakly binds to the 3' splice site of intron 1 of the tropomyosin gene.

PLEASE explain how you got to the answer.

In brain cells, a protein is present that specifically binds to the 3' splice site of intron 1 of the tropomyosin gene. In muscle cells, the protein that binds to the specified 3' splice site is NOT present. Two versions of tropomyosin are generated in humans, the one expressed in brain cells is shorter than the one expressed in muscle cells. Intron 1 3' splice site Intron 2 3' splice site Exon 1 Exon 2 Exon 3 Which of the following represents the components of the mature tropomyosin mRNA in brain cells? a) 5'cap, exon 1, exon 2, exon3, 3' polyA tail b) 5'cap, exon 1, intron 1, exon 2,intron 2, exon3, 3' polyA tail c) 5'cap, exon 1, exon3, 3' polyA tail d) 5'cap, exon 1, exon 2, intron 2, exon3, 3' polyA tail

Explanation / Answer

The protein which binds to the 3' splice site of intron 1 and facilitates alternative splicing is present in brain only not in the muscles.. These protein might be involved in the regulation of exonic splice sites therby facilitating recognition.

Since the alternative spliced form foundin brain is smaller than that of the form found in muscle cells, then this protein might be acting in exclusion of the intron 1.

So the intron 1 will be excised out and the other two exons will be joined. Thus the mature mRNA will have 5' cap exon 1 , exon 3 ,Poly A tail

The gene coding for the protein may be present in both the tissues(brain and muscles), both it is expressed exclusively in brain.

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