A male and a female mouse are each from pure-breeding al...

Question

A male and a female mouse are each from pure-breeding albino strains. They have a litter of 10 pups, all of which have normal pigmentation. The F₁ pups are crossed to one another to produce 56 F₂ mice, of which 31 are normally pigmented and 25 are albino.

Using clearly defined allele symbols of your own choosing, give the genotypes of parental and F₁ mice. What genetic phenomenon explains these parental and F₁ phenotypes?

Accepted Answer

Hi, everyone. Let's look at our next problem. It says in parakeets to jeans, B and Y contribute to two different pigment producing bio synthetic pathways that produce either blue or yellow pigment. The wild type parakeets have feathers that are green with a mixture of blue and yellow. They are also found to have blue feathers due to the absence of yellow pigment, yellow feathers due to the lack of blue pigment and white feathers. The absence of both pigments determine the genotype of the F one progeny when a pure breeding blue parakeet is made into pure, pure breeding yellow parakeet. So I'm just going to highlight genotype of the F one progeny. Pure breeding blue, pure breeding yellow to focus on. We've got a lot of information thrown at us, focus on what we're looking for in the end. So first, let's kind of look at the different possible gene combinations so that we can figure out what our parents are and then what are F one offspring will be? We've got those genes B and Y and we know that wild type parakeets have a mixture of blue and yellow must be co dominant and we'd say that wild type parakeets would be big B blank, big Y blank. They have the presence of both blue and yellow pigment, presumably that is dominant. And then we see that they could be, that would be green. Then they can have blue feathers due to the absence of yellow pigment. So we could call that big B the presence of blue pigment and then blank and then little Y little Y, the recessive little Y being absence of yellow. So we'll call that blue. And then you can also have yellow feathers if there's a lack of blue pigment. So it would be little B little B big. Y you've got yellow and then blank. So that will be yellow and then finally white feathers, the absence of both pigments. That will be our recessive in both little b little b, little y little Y white feathers. So there's our gene combinations And now we say the genotype of the F1 progeny. So the first generation when we have a pure breeding blue, made it to a pure breeding yellow. Well, the phrase pure breeding means generations and generations that have produced nothing but blue. So in that case, we can assume because we've got that, we know that blue can result from um being either homesickness or head for the big B. But in this case, true breeding or pure breeding, we'll assume it's Hamas, I guess dominant. So we're going to call that big B big B little Y little Y then made it to a pure breeding yellow. Again, pure breeding. Meaning will assume that it's homesick is dominant for the yellow alley. Also, we've got little B little B big Y big Y So those are our two parents and our, our cross will be big B big B little Y little Y crossed with little B little B big Y big Y Well, what is our F1 generation? We don't even need to make upon it square here because each parent can only give one type of gamete. Our blue parent is home as I guess dominant for B homicide is recessive for why the only gammy to that parent will give will be big, be little Y the other parent being homesick is recessive for be almost like its dominant for why the only type of gamete it will produces little B big Y. What's the result Of that cross in our F one generation? It's going to be hetero sickos for both genes. Big B, little B big Y little Y. Well, with one dominant allele of each, that entire F one generation will be green. However, we're looking for the genotype and we go back at what we're looking for, which is why it's always good to highlight and focus in on what is our question asking asking for the genotype. So look over our answer choices and we see that choice B is big B little B big y little, y heterocyclic for both traits and therefore answer you in the next video.

Key Concepts

Mendelian Inheritance

Genotype and Phenotype

Punnett Square

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