Feather color in parakeets is produced by the blending of pigments from two biosynthetic pathways shown below. Four independently assorting genes (A, B, C, and D) produce enzymes that catalyze separate steps of the pathways. For the questions below, use an uppercase letter to indicate a dominant allele producing full enzymatic activity and a lowercase letter to indicate a recessive allele producing no functional enzyme. Feather colors produced by mixing pigments are green (yellow + blue) and purple (red + blue). Red, yellow, and blue feathers result from production of one colored pigment, and white results from absence of pigment production.
If F₁ birds identified in part (c) are mated at random, what phenotypes do you expect in the F₂ generation? What are the ratios among phenotypes? Show your work.

Question

Feather color in parakeets is produced by the blending of pigments from two biosynthetic pathways shown below. Four independently assorting genes (A, B, C, and D) produce enzymes that catalyze separate steps of the pathways. For the questions below, use an uppercase letter to indicate a dominant allele producing full enzymatic activity and a lowercase letter to indicate a recessive allele producing no functional enzyme. Feather colors produced by mixing pigments are green (yellow + blue) and purple (red + blue). Red, yellow, and blue feathers result from production of one colored pigment, and white results from absence of pigment production.

If F₁ birds identified in part (c) are mated at random, what phenotypes do you expect in the F₂ generation? What are the ratios among phenotypes? Show your work.

Diagram of two biosynthetic pathways for parakeet feather color production.

If F₁ birds identified in part (c) are mated at random, what phenotypes do you expect in the F₂ generation? What are the ratios among phenotypes? Show your work.

Accepted Answer

Hey, everyone. Let's take a look at this question together. The flower color in a plant is produced by the blending of pigments from two bio synthetic pathways involving three genes which produce three enzymes that catalyze the steps involved in the pathways of pigment production. Flower colors produced by mixing pigments are yellow and purple, pink, red, blue and green flowers result from the production of single colored pigments. While white flowers result from the absence of pigment production. A cross was done between pure breeding plants that produced purple flowers with one producing white flowers. If the F one progeny was self fertilized, determine the phenotypic ratio of the F two progeny. Is it answer choice A A ratio of answer choice B A ratio of answer choice C A ratio of or answer choice D A ratio of 9115. Let's work this problem out together to try to figure out which of the following ratios best describes the phenotypic ratio of the F two progeny. So in order to determine the pic ratio of the F two progeny, we have to first discover what the F one progeny's genotype is in order to do that F one cross. So we can figure out what the phenotypic ratio of the F two progeny is. And so our cross between the parents we know is between pure breeding plants that produced purple flowers and one that is producing white, which we know that those purple flowers are produced by pink and blue, which means that the genotype of the purple flower involves those upper case A's to denote the dominant allele, producing full enzymatic activity of enzyme A, the lower case B because there is no functional enzyme four B. And then that upper case C because of that enzymatic activity. And our white flower is the result of the absence of pigment production, which means that we have those lower case recessive letters or A B and C. And so now that we know the cross of the parents, we are able to predict that F one genotype because we can see that we are cross a homozygous dominant for A with a homozygous recessive or A as well as that homozygous dominant and recessive four C. So we know that we will end up with heterozygous or A and C. However, because B is the same for both parents, the B genotype will remain the same. And so we have our F one cross is denoted as that heterozygous for a homozygous recessive four B and the heterozygous for C. And since the F one progeny, we're self fertilized. That means that our F one cross is a cross between the same genotypes. So we have two individuals with that heterozygous A homozygous recessive B and heterozygous C genotype. Since they are self fertilized, and we can go ahead and set up our rep pundit square for this F one cross to find out what the F two progeny are. So now that we have our pundit square that shows the different genotypes of the F two progeny, we can go ahead and figure out what the phenotypic ratio of the F two progeny is. And based on the information in the pundit square, we know that we have four different phenotypes which are purple, pink, blue and white. And so our genotypes that produce the purple colored flowers are the genotypes in which we have a dominant allele for a and a dominant allele for C because the dominant allele means that we have full enzymatic activity. And so the number of purple flowers that are produced are 123456, 789. So we have nine out of 16 or purple or pink. We have 123 since the pink flowers are those where we only have enzymatic activity in enzyme A and we have three out of 16. And then for blue, we have 123 because the flowers that produce the blue pigmentation are those in which the enzymatic activity is only found in enzyme C, which represents three out of 16. And lastly, we have one that is white because that is the flower that has zero enzymatic activity in all three genes, which is the only one that is homozygous recessive for A B and C. So white, we have one out of 16, which means that our ratio is nine, 331 making answer choice. A the correct answer. Because when we have a cross done of a parent that has enzymatic activity, meaning it has that dominant allele four A and C only. And the parent that produces the white flower has no enzymatic activity in any of its genes. And then when we cross them, we end up with that heterozygous A and C in the F one generation which we then cross with another genotype of the same because it is self fertilized. And we end up with the following F two progeny that gives us that ratio of 9331 or answer choice. A, the correct answer. I hope you found this video to be helpful. Thank you and goodbye.

Verified video answer for a similar problem:

Key Concepts

Gene Interaction and Epistasis

Dominant and Recessive Alleles

Phenotypic Ratios in Mendelian Genetics