Coat color in mice is determined by several independently...

Coat color in mice is determined by several independently assorting autosomal genes. Gene A is involved in the distribution of pigment along the hair. A dominant allele (A) produces a hair color called "agouti" - the hair has dark pigment at the base and tip of each hair shaft and yellow pigment in the middle portion of each hair. Homozygous recessive mice (aa) are missing the yellow portion and thus have solid dark-colored hair. Gene B is involved in the color of the dark pigment. A dominant allele (B) produces black pigment. Homozygous recessive mice (bb) have brown/chocolate-colored hair. Gene C is involved in the production of all pigments. If a dominant allele (C) is present, genes A and B produce pigment. Homozygous recessive mice (cc) are albino. If you cross two mice that are heterozygous for all three genes, what coat color would be the least likely? Select one: a. black agouti b. solid brown c. solid black d. brown agouti e. albino

Transcript

00:01 Answer this question and talk about inheritance.

00:02 It is out -colouring mice is determined by several independently assorting autosomal genes.

00:07 Gene a is involved in a distribution of pigment along the hair.

00:10 A dominant allele a, means this allel here, produces a hair color called a goody.

00:22 So this is the dominant a allele.

00:25 The hair has dark pigment at the base and tip of each hair shaft and yellow pigment in the middle portion of each hair.

00:33 Homocyglysis mice, it means this becessive a allele, are missing the yellow portion and thus have solid dark hair, that dark color hair.

00:43 So practically this is going to be a solid dark colored hair.

00:52 Okay, so this is what we have for the gene a.

00:56 Then we have a gene b that says it's involving the color of the dark pigment.

01:01 A dominant allele b produces black pigment.

01:04 Is a black pigment allele.

01:09 Homocyco -recessive mice means that excessive b is going to have brown chocolate color care.

01:21 And we also have a gene c that says ginc is involving the production of all pigments.

01:27 If a dominant allele c is present, genes a and b produce pigment.

01:32 So this is going to allow a and b to produce the pigment.

01:37 And when you have the recessive c, it is going to, but it is going to call for albino phenotype.

01:45 It says, if you cross two mice that are heterocygous for all three genes, what color would be the least likely? so practically you have this cross here.

01:56 You have this cross where all the genes are heterocylus.

02:05 So you can make three monohyroid panel squares that are going to be like this.

02:16 You're particular crossing this heterocygous a with this heterosegoes a, then this heterocybo's b with this heterocybo c and then this heterocylus c for this heterocybo.

02:27 So you're going to get homozygos, hydrosygos, hydrocegocego, then the same for...

02:35 You're actually going to get the same proportions for the same, for all the crosses here, okay? so this is what you're getting.

02:51 So this is what you're going to have.

02:54 Then it says what code color would be the least likely.

02:59 So we have to look at the options, okay? option a is black aguri.

03:10 So remember that in order to express the a and the b genes, we have to have the dominant c a little present, okay, according to this.

03:19 So what are the chances to have the dominant phenotype for c? you have four possibilities and out of those four you have to have one two and three so three quarters so this is for c in order to express a and b and what are the chances to get it says aguri is dominant a so you have out of four one to three so three quarters two and also black it says black black is dominant b so it is also three quarters so you're going to get a three multiply by three is nine my multiplied by 3 is 27 out of 64...

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