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 the production of one colored pigment, and white results from the absence of pigment production.
What is the genotype of a pure-breeding purple parakeet strain?

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 the production of one colored pigment, and white results from the absence of pigment production.

What is the genotype of a pure-breeding purple parakeet strain?

Diagram of two biosynthetic pathways for parakeet feather color production.

What is the genotype of a pure-breeding purple parakeet strain?

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. Whereas pink, red, blue and green flowers result from the production of single colored pigments. While white flowers result from the absence of pigment production. Note that an upper case letter indicates a dominant allele producing full enzymatic activity and a lower case letter indicates a recessive allele producing no functional enzyme. Determine the genotype of pure breeding plants that produce yellow flowers. Is it answer choice? A big A big A little B little B little C little C answer choice B big A big A big B, big B little C little C answer choice C big A big A big B big B big C big C or answer choice D big A big A little B little B big C big C. Let's work this problem out together to try to figure out which of the following answer choices is the correct answer. So we know that the color of yellow is produced when we combine that red and green, which we can see that the red pigment and the green pigment are produced when all three enzymes r functional. And from the question, we know that full enzymatic activity is indicated by a dominant allele, which is that upper case letter. So in order to figure out which genotype of the plants produce yellow flowers, we need to figure out which answer choice includes all three letters. In that upper case for the dominant allele, since we need all three enzymes producing full enzymatic activity. So looking at our answer choices, we can see that answer. Choice C is the only answer choice here in which all three alleles are all dominant, which produce that full enzymatic activity and give us those yellow flowers. Though answer choice C homozygous dominant. A homozygous dominant B and homozygous dominant C is the correct answer because in answer choice A, we can see that B and C are not dominant and answer choice BC is not dominant and, and, and answer choice DB is not dominant. So answer choice A B and D are all incorrect. Since answer choice C is the only one where all three alleles are dominant, producing that full enzymatic activity which gives us those yellow flowers. So answer choice C homozygous dominant for a homozygous dominant for B and homozygous dominant for C is the correct answer I hope you found this video to be helpful. Thank you and goodbye.

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Key Concepts

Genotype and Phenotype

Dominant and Recessive Alleles

Biosynthetic Pathways