A species of mice can have long or short tails. If you crossed a male mouse which is heterozygous and has a long tail with a female mouse with a short tail, what would the expected phenotypic outcome be and why?

A)
100% long tails due to the Law of Dominance.

B)
There is no way to predict the phenotypic ratio since one of the parents is heterozygous.

C)
75% long tails and 25% short tails because the dominant allele for long tail still masks the recessive short tail allele.

D)
50% long tails and 50% short tails because the heterozygous genotype increases t

Question

A species of mice can have long or short tails. If you crossed a male mouse which is heterozygous and has a long tail with a female mouse with a short tail, what would the expected phenotypic outcome be and why?
	

A)
	100% long tails due to the Law of Dominance. 	
	

B)
	There is no way to predict the phenotypic ratio since one of the parents is heterozygous. 	
	

C)
	75% long tails and 25% short tails because the dominant allele for long tail still masks the recessive short tail allele. 	
	

D)
	50% long tails and 50% short tails because the heterozygous genotype increases t

blues · Answer

OK, the first nugget of useful info in the problem is that a heterozygous mouse - that is, a mouse with one allele for a long tail and one allele for a short tail - has a long tail. That tells us that the allele for long tail is dominant and the allele for short tail is recessive.


So if you crossed a heterozygous mouse (Tt) with a short tailed mouse (tt) where T indicates a dominant, long tail allele and t indicates a recessive, short tail allele, what do you get?

blues · Answer

The cross is Tt x tt. It will help you to set up a Punnett Square with the Tt on one side and the tt on the other:

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