In the rats identified in Problem 10, a third independen...

Question

In the rats identified in Problem 10, a third independently assorting gene involved in determination of coat color is the C gene. At this locus, the genotype C– permits expression of pigment from genes B and D. The cc genotype, however, prevents expression of coat color and results in albino rats. For each of the following crosses, determine the expected phenotype ratio of progeny.

BbDdCC×BbDdCC

Accepted Answer

Well, good back everyone. Let's look at our next question. When a tall pea plant with round seeds, big T big T big A big R was crafted with a crossed with a dwarf pea plant with wrinkled seeds, little tea, little tea, little R, little R where T stands for dominant tall, big T stands for dominant, tall and little tea for recessive dwarf height and big R for dominant round and little R for recessive wrinkled sheet seed shape. The results were as follows. The individual F one populations all possessed tall round seeds. However, self pollination among F one individuals resulted in a phenotypic ratio of 9 to 3 to 3 to 1. This ratio is caused by which of the following principles. Choice. A law of dominance, choice B law of segregation, choice C law of independent assortment and choice D, none of these. But when we think about this phenotype ratio 9 to 3 to 3 to 1 in our F two generations. So F one crossed with F one, the phenotypes in this ratio would be in the nine having both the dominant traits. Each of the three is having one dominant and one recessive trait and the one having both recessive traits. Well, when we look back at where these came from, we know that our original parents or original source for these plants are homozygous dominant for both traits and homozygous recessive for both traits. And yet here we have in the second generation, we have the dominant recessive mixed up. So we started with two dominant traits together and two recessive traits together. But then we end up with one of each type of trait. So that would be our law of independent assortment because it means that the two genes are not necessarily inherited together. So you don't have to have big T and Big R narrative together. You could have big T and little R or little T and big R, they assort independently of each other. But let, let's look at our other answer choices to understand why they're not correct. Well, choice D we can eliminate right away. None of these because choice C is correct. Choice. A, the law of dominance refers to a dominant trait, masking the expression of a recessive one. Well, that would explain why in our F1 generation, we only see the dominant trait, the dominant trait is masking the expression of the recessive one in both traits. But that doesn't explain why. Then in the F- 2 generation, we see this ratio including mixed up combinations as compared to the parents. So choice A is not correct. And then finally, choice. B the law of segregation. Well, this refers to the fact that offspring inherit one ally from each parent, those two owls separate from each other before the actual mating occurs. So that would explain why we see in, say a mono hybrid cross, you see your first generation only showing the dominant traits and you see the recessive traits reappearing in the second generation because in that second generation, you have some individuals who inherit a recessive trait from each parent and display that recessive trait when you didn't see that in the previous generation. So log of law of segregation um just refers to the fact that you get one all, all from each parent. It doesn't explain those mixed up phenotypes. So that's why that's not our correct answer. So again, self pollination among F one individuals giving us a pen atypic ratio of 9 to 3 to 3 to 1. This ratio is caused by which of the following principles. And our answer is choice c the law of independent assortment. See you in the next video.

Key Concepts

Independent Assortment

Genotype and Phenotype

Punnett Square

Watch next