You are investigating two hypothetical traits in cows: theability to sing and th

Question

You are investigating two hypothetical traits in cows: theability to sing and the ability to talk to ants. Both ofthese traits are recessive to the wildtype (not singing or talkingto ants). Since both of these mutations involve vocalization,it is possible that they are encoded by alleles of the samegene. You must also consider the possibility that the traitsare encoded by alleles of different genes, which may or may not belinked. If a true breeding singing cow is crossed to a truebreeding cow that talks to ants, what are the parental genotypesand F1 progeny phenotypes and genotypes expected in each of thefollowing cases:

a. The mutations are alleles of linked genes. Explainanswer.

b. The mutations are alleles of the same gene. Explainanswer.

c. The mutations are alleles of unlinked genes. Explainanswer.

Assume complete penetrance for both traits, and assume thatepistasis does not occur.

Thanks Lark! There is an additional part of the question Iforgot to put down. I was wondering if you could help mesolve it.

Here's the additional question:

"If a testcross between a singing, ant-talking cow and one of thewildtype F1 progeny described above is performed, what F1 progenyphenotypes and genotype ratios are expected if:

d. The mutations are alleles of linked genes. Explainanswer.

e. The mutations are alleles of unlinked genes. Explainanswer."

Explanation / Answer

Suppose the ability to sing is encoded by the 's' allele and thewildtype is encoded by the 'S' allele. Also suppose the ability to talk to ants is encoded by the 't'allele and the wildtype is encoded by the 'T' allele. A singing and ant talking cow would have genotype: st st A wildtype cow would have genotype: ST ST A cross would look as follows:       |        ST     ST St   |        stST       st ST St   |      stST       st ST So the progeny all have genotype, st ST, which results in thenormal wildtype phenotype. e) A singing and ant talking cow would have genotype: ss tt A wildtype cow would have genotype: SS TT Punnett Square s s t t x S S T T st st st st ST SsTt SsTt SsTt SsTt ST SsTt SsTt SsTt SsTt ST SsTt SsTt SsTt SsTt ST SsTt SsTt SsTt SsTt So all the progeny have genotype SsTt which is the wildtypephenotype just like in the previous part. (All the genotypes of theF1 generation are the same for part D and E, however the F2generations would look totally different.)

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