A gene has two alleles B and b. B is responsible for the expression of character x. b is responsible for the expression of character y. B is completely dominant over b. Another gene A is epistatic on

Question

A gene has two alleles B and b. B is responsible for the expression of character x. b is responsible for the expression of character y. B is completely dominant over b. Another gene A is epistatic on gene B. When A is in the dominant condition it suppresses the expression of B and b and gives rise to character z. In recessive condition (allele a) allows expression of B and b. When an organism with genotype AaBb is crossed with another organism with genotype AbBb, the ratio of characters x, y and z seen in its offsprings is

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According to the data given,

Character x will be expressed in organisms having genotypes aaBB or aaBb. Character y will be expressed in organisms having genotypes aabb. Character z will be expressed in organisms having genotypes $A A B B, A A B b, A A b b, A a B B, A a B b$ and $A a b b$

The cross $A a B b x A a B b$ will produce,
$A A B B, A A b b, a a B B, a a b b, A a B B (2), A A B b (2), A a b b (2), a a b (2)$ and AaBb (4).

Thus, Character x will be expressed in $a a B B (1) a n d a a B b (2)$ that is 3 out of 16 possibilities

Thus, Character y will be expressed in $a a b b (1)$ that is 1 out of 16 possibilities

Thus, Character z will be expressed in $A A B B (1), A A B b (2), A A b b (1), A a B B (2), A a B b (4) a n d A a b b (2)$ that is 12 out of 16 possibilities

The ratio of $x : y : z = 3 : 1 : 12$

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