Question

Among the progenies born from the mating of a white and an Andalusian (blue) fowl, there are 15 white chickens. What is the expected total number of progeny?

• A. 30
• B. 15
• C. 45
• D. 60

Answer 1

The correct option is A 30

Andalusian fowl is one of the breeds of domestic chicken, which is an example of incomplete dominance. Andalusian fowl have two pure forms black and white. When these pure lines (BB×bb) are crossed, the heterozygous $F_1$ progeny (Bb) appears blue due to the occurrence of fine black and white stripes on the feathers. The homozygous phenotypes have blended. When $F_1$ is crossed with each other, progeny displays 1:2:1 ratio phenotypically as well as genotypically. $\frac{1}{4}$ of $F_2$ progeny are Black (BB), $\frac{2}{4}$ of are blue (Bb) and $\frac{1}{4}$ progeny are white (bb).
Now, when an Andalusian (Bb) is crossed with white chicken:
Parents (Andalusian)B × bb (white)
Gametes B b b b
Progeny Bb, Bb, bb, bb
Half of the progeny are Andalusian and half of the progeny will be white. So, the total number of progeny would be just double that of any of the progeny.
Given the number of white chicken = 15
Therefore, the total number of progeny = 2 × 15
= 30