Scenario: A hypothetical population of snails exists that exhibit several intere

Question

Scenario:       A hypothetical population of snails exists that exhibit several interesting characteristics.  The snail shells range in size from 5mm in diameter up to 10 mm in diameter.  The median size is 6 mm.  In very sandy areas shells tend to be smaller, in rocky areas the shells tend to be larger and thicker.  Shell color is controlled by a single gene, with possible genotype/phenotypes of DD= dark brown, Dd= light brown, dd= light tan.  A second gene controls banding (B,b), with snails having either 2 or 5 bands.  Snails with 5 bands always produce offspring with 5 bands while snails with 2 bands can produce offspring with 5 bands.This gene has been sequenced with the following sequences noted:

Gene for 2 bands

AGA   TTC   CTT

Gene for 5 bands

AGA   TTG   CTA

Which allele for band number is dominant, the 2 band allele or 5 band allele?

Gene for 2 bands

AGA   TTC   CTT

Gene for 5 bands

AGA   TTG   CTA

Explanation / Answer

Gene for 5 bands allele is dominant over gene for 2 bands. As snails with 5 bands always produce offspring with 5 bands never offspring with 2 bands. But in other hand snails with 2 bands can produce offspring with 5 bands. It may be due to the presence of the gene for 5 bands with the gene for 2 bands in heterozygotic condition. Here gene for 5 bands represses the expression of the gene for 2 bands, for that the function of the gene for 2 bands musked by the gene for 5 bands. So, in both homozygote and heterozygote condition gene for 5 bands produce only 5 bands offspring and the gene for 2 bands only can produce in homozygotic condition.

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