The coat color in mink is controlled by two codominant a...

Question

The coat color in mink is controlled by two codominant alleles at a single locus. Red coat color is produced by the genotype R₁R₁, silver coat by the genotype R₁R₂, and platinum color by R₂R₂. White spotting of the coat is a recessive trait found with the genotype ss. Solid coat color is found with the S– genotype.

If the cross SsR₁R₂ x SsR₁R₁ is made, what are the progeny phenotypes, and in what proportions are they expected to occur?

Accepted Answer

Hello, everyone. Let's look at our next question. It says, suppose we cross pollinate white and red variants of Hibiscus rosa sinensis. If they produce a pink variant, this event is referred to as. So we have two different color variants and the offspring they produce, which was expected to be heterocyclic have a genotype that's intermediate between the parents. So when we think about this type of inheritance where you see this intermediate phenotype, what terminology are we looking for? When we look at our answer choices, we have choice, a co dominance, choice be incomplete, dominance, choice, see dominance and choice D recessive. Well, we can go ahead and eliminate choice C and choice D dominance and recessive because in dominant or recessive inheritance, you have complete masking of the recessive allele. So you would see the offspring and across between the two extremes showing only one trait. Um So that's clearly not what's happening here. And we're not seeing white or red only. We're seeing this intermediate phenotype, but co dominance and incomplete dominance can be a little trickier to distinguish between. So I'm just going to put up sort of the definitions of both of them So we can look at them in comparison. Co dominance is when you have both alleles simultaneously expressed, the dominant and recessive traits are both seen sort of side by side for lack of a better word examples of this would be a speckled chickens where you have chickens that have inherited black, a gene for black feathers and a gene for white feathers. And they come out speckled, there's both black and white feathers, they're not gray chickens, they're speckled. Another example that might not appear right away to be like, this would be the color, um Rhone in a cow or a horse. And this occurs, um, when these animals have inherited a gene for a red coat and a gene for the white coat and they're both expressed together, resulting in an animal that has some hairs that are red and some hairs that are white, all mixed together. And the only reason it's a little tricky example is from a distance and the reason it has its own color name, um, the animal looks almost pinkish are very, very light red. So it almost, you know, from appearance might look like it's an intermediate phenotype, but it's not actually, it's caused because the hairs are very fine. It's caused by both the red and white hairs being present together, but each individual hair is either red or white like the speckled chickens. Then this is as opposed to incomplete dominance and incomplete dominance. The offspring has a different phenotype from either the dominant or recessive trait. That's intermediate between the two phenotype. So it's not both traits being expressed sort of side by side. It's an intermediate phenotype. So we're looking at these flowers, they're pink flowers in their hair is, I guess the whole flower is pink. It's not speckled red and white or spotted red and white. So what we're looking for here is incomplete dominance. And so that's going to be choice B and we will eliminate choice A co dominance. So again, if we cross pollinate the red and white variants and they produce a pink variant, this event is referred to as choice be incomplete dominance. See you in the next video.

Key Concepts

Codominance

Genotype and Phenotype

Punnett Square

Watch next