Flower Color & Soybeans

Question

Flower color in soybean is inherited independent of pubescence color. Brown pubescence is dominant to grey pubescence color. The probability of purple flower color is not influenced by whether or not the pubescence color is brown or grey. The probability of brown pubescence is 3/4 and of grey is 1/4. The probability of a purple flower color is 3/4 and of white is 1/4.

If an AaBb plant is crossed to a AaBb plant, what is the probability of a white flower grey pubescence plant?

P (A_) = 3/4           P (aa) = 1/4
P (B_) = 3/4           P (bb) = 1/4

P (aa) x P (bb) = 1/4 x 1/4 = 1/16 = P (aabb)
P (A_) x P (B_) = 3/4 x 3/4 = 9/16 = P (A_B_)
P (A_) x P (bb) = 3/4 x 1/4 = 3/16 = P (A_bb)
P (aa) x P (B_) = 1/4 x 3/4 = 3/16 = P (aaB_)

P (aa) x P (bb) is multiplication of independent events.

P (aabb) + P (A_B_) + P (A_bb) + P(aaB_)
is addition of mutually exclusive events.