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posted by  YAY on 10/9/2008 12:36:36 AM  |  status: Live  

exons and introns

Course Textbook Chapter Problem
Genetics N/A N/A N/A
Question Details:

The CCR5 gene consists of 5 exons (numbered from 1 to 5 in the 5’ to 3’ direction of the RNA transcript) and 4 introns (numbered 1 to 4 in the 5’ to 3’ direction). The CCR5-Δ32 allele arises from a 32 base pair deletion in the CCR5 gene. The protein product of the CCR5-Δ32 gene is non-functional. If the deletion is increased by one base pair then the resulting CCR5-Δ33 gene product is functional. The Δ32 deletion is most likely to be located in which region of the CCR5 gene?

A) 5’ untranslated region

B) Exon 1

C) Intron 1

D) Intron 4

E) Exon 5

why??????

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posted by aegio on 10/14/2008 5:02:23 AM  |  status: Live
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Response Details:
I spent some time trying to come up with answer for you but I'm not exactly sure. Did you every find out an answer? I am curious.

I figured that the 32 base pair was taking out most of an intron. Thus, the parts of the intron that tell the spliceosome where to cut were missing and the protein could not fold properly with the piece of intron in there.
The 33 base pair deletion completely removes the intron, therefore, it does not interfere.

I don't know if it would be intron 1 or 4...
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posted by jaydee on 10/15/2008 5:55:05 PM  |  status: Live
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Response Details:
First off it must occur in the exon because the introns are not translated into the protein product. The 33 bp deletion results in a functional protein product because it just deletes a section of the amino acids to be translated as codon for amino acids are in base pair triplets. The 32 bp deletion causes a frameshift that results in a nonfunctional product. The difficult question is whether its on exon 1 or exon 5.
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