Imagine that long fins in zebrafish is a dominant trait. A breeder wants to set up a breeding program beginning with homozygous dominant long-finned fish. If she obtains a handful of the long-finned fish, how can she tell which if any of these are homozygous for the trait? A. Cross the long-finned fish with short-finned fish; if three-fourths of the offspring are long-finned and one-fourth are short-finned, the long-finned parent is homozygous. B. Cross the long-finned fish with short-finned fish; if half the offspring are long-finned and half are short-finned, the long-finned parent is homozygous. C. Cross the long-finned fish with short-finned fish; if four-fifths of the offspring are long-finned and one-fifth are short-finned, the long-finned parent is homozygous. D. Cross the long-finned fish with short-finned fish; if the offspring are all long-finned, the long-finned parent is homozygous.

Question

Biology

Lorena Carrillo

5 August, 06:59

Imagine that long fins in zebrafish is a dominant trait. A breeder wants to set up a breeding program beginning with homozygous dominant long-finned fish. If she obtains a handful of the long-finned fish, how can she tell which if any of these are homozygous for the trait? A. Cross the long-finned fish with short-finned fish; if three-fourths of the offspring are long-finned and one-fourth are short-finned, the long-finned parent is homozygous. B. Cross the long-finned fish with short-finned fish; if half the offspring are long-finned and half are short-finned, the long-finned parent is homozygous. C. Cross the long-finned fish with short-finned fish; if four-fifths of the offspring are long-finned and one-fifth are short-finned, the long-finned parent is homozygous. D. Cross the long-finned fish with short-finned fish; if the offspring are all long-finned, the long-finned parent is homozygous.

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Answers (1)

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Abel Herring · Answer 1

D - Cross the long-finned fish with short-finned fish; if the offspring are all long-finned, the long-finned parent is homozygous.

Explanation:

Since long fins is a dominant trait, a cross between homozygous dominant long-finned fish and short-finned fish should results in all long-finned offspring.

If long fin allele is L, homozygous long fin will be LL and short fin will be ll

LL x ll

This will result in Ll, Ll, Ll, Ll genotype offspring and since L is dominant, all the offspring will have long fin.

Hence, in order to for the breeder to tell which of the long-finned fish is/are homozygous for the trait, all she needs to do is mate each of the long-finned fishes with a short-finned fish. Anyone that yields all long-finned offspring is homozygous for the trait.

The correct option is D.