Two pure-breeding wheat strains, one producing dark red kernel...

Question

Two pure-breeding wheat strains, one producing dark red kernels and the other producing white kernels, are crossed to produce F₁ with pink kernel color. When an F₁ plant is self-fertilized and its seed collected and planted, the resulting F₂ consists of 160 plants with kernel colors as shown in the following table.

If an F₁ plant is crossed to a dark red plant, what are the expected progeny phenotypes, and what is the expected proportion of each phenotype?

Table displaying the number of wheat plants by kernel color: white, dark red, red, light pink, and pink.

If an F₁ plant is crossed to a dark red plant, what are the expected progeny phenotypes, and what is the expected proportion of each phenotype?

Accepted Answer

Hello everyone and welcome to today's video. So, flower color in a plant X is determined by a gene with two alleles, one for red flowers and one for white flowers. When a pure breeding or a pure breed having red colored flowers is crossed with a pure breed of white colored flowers. All the resulting offspring are pain color in the F one generation which upon so fertilization gives a 1 to 2 to one phenotypic ratio of red to pink to white flowers in the F two generation. So from the above experiment, which of the following conclusions can be drawn as answer choice A, we have the capitalized or A is completely dominant over the lower case or A B states. The lowercase R A is completely dominant over the capitalized R A C. We have the capitalized R A is partially dominant over the lowercase R ad we have the upper case R and case or a exhibit co dominance. Well, in order to solve this problem, we need to understand that one of the parents is going to be these homozygous dominant for art this red flower. While the other one is going to be this homozygous recessive for art or this white flour. But once they mate the offspring in the f one generation is going to be pink being heterozygous. Now, this really doesn't make sense at first. Why is it pink? Why is it either red or white or there is this phenomenon called incomplete dominance were either where no a leo is going to be completely dominant over the other. And instead they're both going to contribute to the phenotype with only one A V V in partially dominant over the other. And this is why we get pink flowers in our F two generation. Now that we know this, let's go over each of our answer choices so that we may determine the correct one first, we have A and B. So the upper case R O is completely dominant over the lowercase R O or the lower case R O is completely dominant over the uppercase R O. Well, we determine that we have this incomplete dominance and therefore no A is going to be completely dominant over the other. There is only going to be one, partially dominant ali, but they're both going to contribute to the phenotype because of this, both of these answer choices are incorrect and we're going to cancel them out. Then we have D the upper case R and lower case or ao's exhibit codominance. Now, codominance is another phenomenon where they're both contributing to the same phenotype, but it's not a combination they're rather both appearing. But this is not what we're seeing here in the question. So we're going to cancel this out as well. And then we have CD R AO is partially dominant, not as partially dominant, not completely dominant over the lower case R A. This is what we're seeing here in incomplete dominance. And therefore, we're going to highlight answer choice C the upper case R O is partially dominant over the lower case R O as the final answer to this question, I really hope this video helped you and I hope to see you on the next one.

Key Concepts

Mendelian Inheritance

Phenotypic Ratios

Punnett Square

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