Precursor-> Intermediate 1-> Intermediate 2-> intermediate 3-> product white A w

Question

Precursor-> Intermediate 1-> Intermediate 2-> intermediate 3-> product
white A white B yellow 2 C light green D teal
Consider the above biological synthetic pathway for feather color in a rare species of parakeet. A, B, C and D are dominant forms of four genes. The recessive alleles a, b, c and d express non-functional enzymes. functional gene products proteins are required for each of the individual reactions to occur
what is a possible genotype that would result in parakeets with these colors : teal, or yellow feathers, and the recessive mutant allele b is epistatic to which of the other alleles
B) what would be the phenotypic ratio of the offspring from the following cross, must write the phenotype answer AABbCCdd x aaBbccDd

Explanation / Answer

In the above pathway, each gene is responsible for a step, and product forms only when all th egenes are active in expression.

A, B, C, D are functional genes, and a, b, c, d are non functional enzymes.

A) Its given that A - white, B- yellow, C- light green, D- teal

Possible genotypes for teal is that Dd or DD.

or yellow feathers - Bb or BB, and if A, B , C, D in a linear fashion in pathway, then the C and D genes must be non functional - AaBbccdd, or AABBccdd

B) AABbCCdd x aaBbccDd

Progeny are

AaBBCcDd - product formed

AaBbCcDd - product formed

AaBbCcDd - product formed

AabbCcdd - pathway takes place upto intermediate 1 only.

Phenotypic ratio is 3: 1

Hope it helps.

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