The dorsal pigment pattern of frogs can be either 'leopard' (w...

Question

The dorsal pigment pattern of frogs can be either 'leopard' (white pigment between dark spots) or 'mottled' (pigment between spots appears mottled). The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations, and a pair of reciprocal crosses is performed. The cross results are shown below.

Cross 1: P₁: Male leopard x male mottled

F₁: All mottled

F₂: 70 mottled, 22 leopard

Cross 2: P₁: Male mottled x female leopard

F₁: All mottled

F₂: 50 mottled, 18 leopard

Which of the phenotypes is dominant? Explain your answer.

Accepted Answer

Hi, everyone. Let's look at our next question. If a Hamas, I guess yellow, big Y big Y P plant is crossed with homos, I guess. Green little Y little Y P plant. What is the phenotype of the dominant plant in the F two generation? So we have to Hamas, I guess parents being crossed to start with big Y big Y little Y little Y Well, in the F one generation, all of the offspring will be headed this big Y little Y because each parent can only donate the alley. They have each parent is homeless. Vegas. So that will be the F one generation. But we're looking at the F two generation and saying, what is the dominant phenotype? Let's remember that because we want to look at phenotype. So we're gonna put up a pen it square. We just use our four box punnett square since we've got just the one trait here. So we know that in the F two generation, we're crossing the offspring of the F one generation. So all of the individuals will be big. Y little Y put that across the top for one parent. Big Y little Y on the side for the other parent. And now let's fill in the offspring. It is helpful for problems like this rather than having to draw the square each time. This is a mono hybrid cross. And we can remember that the ratio of gina types of the offspring will be 1 to 2 to one of the one homogeneous dominant to hetero. Guess one homos, I guess, recessive. So that can be useful thing to remember if you don't want to draw out your pocket square each time. But we'll just confirm that with our punnett square, we've got one square homos, I guess dominant big Y big Y then two squares with hetero cygnus big Y little Y and one square home as I guess, recessive little Y little Y. So there's our gina types, but we're looking for the phenotype, the dominant phenotype in the f two generation. Well, every offspring carries one big Y at least one big Y allele will be yellow. So if we highlight the genotype of the yellow plants, that would be our home is dominant and our heterocyclic, it's, we get three out of four being yellow. So the yellow phenotype will be dominant. So we look over here and that's choice. A yellow pea plant. Well, look at our other answer choices just to understand why they're not correct choice be green pea plant. We'll, we'll have some green pea plants but only 1/4 of the offspring roughly. But that's not correct. I see equal dominance. Um that's not correct because the majority of our F2 plants will be yellow and choice D data is insufficient. That's not correct. As we do have enough data with the genotype of the parents of these crosses to give us that prediction. So choice D is not correct. So again, when we forgot, a homogeneous yellow pea plant crossed for the homosexuals green pea plant. What is the phenotype of the dominant pea plant in the after generation? Choice? A yellow pea plant? See you in the next video.

Key Concepts

Dominance in Genetics

Phenotypic Ratios

Reciprocal Crosses

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