As we learned in this chapter the white mutation...

As we learned in this chapter, the white mutation of Drosophila studied by Thomas Hunt Morgan is X-linked and recessive to wild type. When true-breeding white-eyed males carrying this mutation were crossed with true-breeding purple-eyed females, all the F1 progeny had wild-type (red) eyes. When the F1 progeny were intercrossed, the F2 progeny emerged in the ratio 3/8 wild-type females: 1/4 white-eyed males: 3/16 wild-type males: 1/8 purple-eyed females: 1/16 purple-eyed males. a. Formulate a hypothesis to explain the inheritance of these eye colors. b. Predict the F1 and F2 progeny if the parental cross was reversed (that is, if the parental cross was between true-breeding white-eyed females and true-breeding purple-eyed males).

Transcript

00:04 You know, not to answer this question.

00:05 Let's talk about inheritance.

00:06 It says, as you know, fruit flies normally have red eye color, that is the wild type.

00:11 In the 19s, thomas hunt morgan and his students discovered the famous white -eyed mutation, which is ex -linked.

00:20 The gene is responsible for pigment attachment.

00:22 Therefore, the excessive white mutation, homocygo -resensive in female or hemicygos in males, is epistatic to any other eye color traits such as autosomal brown or cilia.

00:35 So let's first state that the genotypex and phenotype here for both genes, okay? when you get, this is female, you remember, and this is male.

00:47 So in case of the x -link gene here, when you get the dominant trait, it means the homocygous dominant or the heterocygose like this, we're going to get normal pigmentation, and you're going to express the second gene.

01:03 So you're going to have here normal pigmentation.

01:11 The same for the same for the males, okay? but when you have the homocylusive here, you're going to get white eye color and the same here.

01:24 Okay, and it doesn't matter what genotype you have for the second gene because it is going to be directly have white eye color.

01:32 So the second gene here is going to be, this used to be a nomenal.

01:37 So you have the homozygous dominant, heterocygous here.

01:42 You're going to have that they are going to code for the wild type that is great eye color, well it's just white that like this, white type.

01:52 And the homozygos is if it's going to be brown.

01:56 So in this case it says, a brown eyed drosophila male, it means a brown eye like this.

02:04 If this male is brown, it means that it is expressing pigment, and hence it is going to be, like this.

02:15 Okay, so this male is going to be crossed with a white -eyed drosophila female.

02:22 It means a white -eyed drosophila female like this, who is not a carrier of brown mutation.

02:31 It means that is like this.

02:34 I'm sorry, like this.

02:39 So this is the cross and it says, what is the male genotype and what is the female genotype? so, well, this is the male genotype and this is the female genotype...

Question

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