Question

5. Some dogs bark while trailing, others are silent. The barking trait is due to a dominant gene. Erect ears are dominant to drooping ears. What kind of pups would be expected from a double heterozygous erecteared, barker mated to a droopedeared, silent trailer?
Gene B controls the barking ability; gene E controls ear shape. Let B be the dominant allele for the barking trait. Let b be the recessive allele for the silent trait. Let E be the dominant for erect ears. Let e be the recessive allele for drooping ears.

Answer 1

As given in the question, Gene B controls the barking ability; gene E controls ear shape. Let B be the dominant allele for the barking trait. Let b be the recessive allele for the silent trait. Let E be the dominant for erect ears. Let e be the recessive allele for drooping ears.

Hence the heterozygous genotype for erect eared, barker is EeBb and the gametes that they produce are: EB, eB, Eb and en and the genotype for drooping eared, silent is eebb and the gametes they produce is only eb. A cross between them is indicated in the following table:

	EB	eB	Eb	eb
eb	EeBb Erect eared, barker	eeBb Dropping ear, barker	Eebb Erect eared, silent	eebb Drooping ear, silent

Hence the pups produced by this cross are: erect ear, barker:drooping ear, barker:erect eared, barker:dropping ear, silent:erect ear, silent= 1:1:1:1.

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