Question

On the planet Kermit, in the Muppet population, there are two autosomal loci of interest. The first locus has alleles A and a, and the second locus has alleles B and b. A and B are the dominant alleles at the respective loci. The loci act in an epistatic manner, identical to the way two genes interact to produce coat color in labradors. The phenotype here is muppet hair color. We have the following results:
Muppet hair color as a function of two-locus genotypes

Two-locus genotype Muppet hair color
A_B_ Cookie monster blue
aaB_ Elmo red
__bb Janice blonde

If two doubly-heterozygous Cookie-monster blue-haired muppets mate, and produce 1000 children, which of the follow values most closely represents the expected number of Janice blonde-haired offspring?

a. 12.
b. 260.
c. 252.
d. 512.
e. 240.

Answer 1

Answer:

The values that most closely represent the expected number of Janice blonde-haired offspring is 252 individuals, option C.

Explanation:

Available data:

• Two diallelic genes acting in a recessive epistatic manner to express hair color
• Allele A is dominant over the allele a
• Allele B is dominant over the allele b
• A_B_ Cookie monster blue
• aaB_ Elmo red
• __bb Janice blonde

When talking about epistasis, we are referring to an interruption. These are interactions between genes located in different loci in the same chromosome. An epistatic gene can alter, influence, or suppress the expression of a hypostatic gene. When the epistatic gene is recessive, the interaction is known as recessive epistasis.  

Observing the altered phenotype proportions of the offspring can reveal which interaction is operating in the trait determination.  

In recessive epistasis, the proportion is 9:3:4.

Cross: Between two doubly-heterozygous

Parentals) AaBb    x    AaBb

Phenotype) Cookie-monster blue-haired individuals

Gametes)  AB, Ab, aB, ab

                 AB, Ab, aB, ab

Punnett square)     AB       Ab        aB         ab

                 AB      AABB    AABb  AaBB    AaBB

                 Ab      AABb    AAbb   AaBb    Aabb

                  aB     AaBB     AaBb   aaBB    aaBb

                  ab     AaBb      Aabb   aaBb    aabb

F1) 1000 individuals

     9/16 individuals are expected to be Cookie-monster blue-haired, A-B-

     3/16 individuals are expected to be Elmo Red, aaB-

     4/16 individuals are expected to be Janice blond, A-bb + aabb

16 ------------------------------------------- 1000 individuals

4 Janice blond individuals ---------- X = 250 individuals

So, 250 individuals are expected to be Janice blonde. The observed number might vary a little bit from this value.  The values that most closely represent the expected number of Janice blonde-haired offspring is c = 252 individuals