An inbred strain of plants has a mean height of 24 cm. A...

Question

An inbred strain of plants has a mean height of 24 cm. A second strain of the same species from a different geographic region also has a mean height of 24 cm. When plants from the two strains are crossed together, the F₁ plants are the same height as the parent plants. However, the F₂ generation shows a wide range of heights; the majority are like the P₁ and F₁ plants, but approximately 4 of 1000 are only 12 cm high and about 4 of 1000 are 36 cm high.

What mode of inheritance is occurring here?

Accepted Answer

Hello everyone and welcome to today's video. So today, we need to assume that the height of a tree is controlled by three polys. It has a maximum height of 20 m and a minimum height of five m, determine the height of a tree with the fully heterozygous genotype. So as answer choice A we have five m as answer choice B we have 12. m as answer choice C we have 17.5 m and as answer choice D we have 20 m. So in order to determine the contribution of each polygene, when we have three, we're going to use the following formula. It's going to be the maximum height minus the minimum height divided by the number of polys. So this is going to be 20 minus five divided by six, which is going to be equal to 2.5. Now, we have this contribution of each polygene. Now we need to solve the contribution of the dominant polygene in the tree having the fully heterozygous phenotype because remember that this dominant phenotype is what's going to be expressed. Therefore, it is going to be given by multiplying the 2.5 that we obtain here, the contribution of each polygene by the number of the dominant genotypes, which is going to be three. So this is going to be equal to 7.5. So now we have the contribution of only the dominant polygene in the tree. Now, we need to add this to the minimum height in order to obtain the height of this fully heterozygous tree, which is going to be 7.5 plus the minimum height, which is five m. And this is going to be 12.5 m. And this is going to be the height of the tree with a fully heterozygous genotype 12.5. If we look at our answer choices, this is going to be answer choice B 12.5 m. I really hope this helped you and I hope to see you on the next one.

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