A three-gene system of additive genes (A, B, and C) controls plant height. Each gene has two alleles (A and a, B and b, and C and c). There is dominance among the alleles of each gene, with alleles A, B, and C dominant over a, b, and c. Under this scheme, the dominant genotype for a gene contributes 10 cm to height potential, and the recessive genotype contributes 4 cm. What is the height potential of a plant that is homozygous for all three dominant alleles?

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Accepted Answer

Hey, everyone. Let's take a look at this question together. A gene controls the length of the tail feathers in a bird species. The allele for long tail feathers is dominant over the allele for short tail feathers. A heterozygous bird is crossed with a homozygous recessive bird. What is the probability of obtaining offspring with long tails? Is it answer choice? A one out of two answer, choice, B one out of four answer choice, C one out of eight or answer choice D one out of six, let's work this problem out together to try to figure out which of the following are the probability of obtaining offspring with long tails. So we know that the long tail feather allele is dominant over the short tail feathers allele. And we have our heterozygous bird that is crossed with the homozygous recessive bird. So that means that we are crossing that heterozygous bird, which has the dominant T allele and the recessive T allele. And they are crossed with the homozygous recessive bird. So they have two recessive T alleles and we have to set up upon a square in order to determine the probability of their offspring. And we can see from the punt square that we have on the screen, 50% of the offspring will be heterozygous and 50% of the offspring will be homozygous recessive, which means that 50% of the offspring will have those long tail feathers. And 50% of the offspring will have the short tail feathers. Since the heterozygous individuals will produce the long tail feathers. And the homozygous recessive individuals will produce those short tail feathers. So that means that the probability of obtaining offspring with long tails is 50%. So answer choice. A one out of two is the correct answer. Since we know that two of the four offspring in the pond and square have those long tails. And when we reduce that two out of four, we end up with one out of two, which is answer choice. A I hope you found this video to be helpful. Thank you and goodbye.

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Key Concepts

Additive Gene Action

Dominance and Alleles

Genotype and Phenotype Relationship