4. Cross a white bull with a white cow. Show the Punnett Square: % Red Cow
% Roan Cow
% White Cow

100% white cow

Explanation:

This question involves a single gene coding for skin color in cattle. The allele for red color (R) is codominant with the allele for white color (r). Hence, the roan cattle (Rr) will possess both red and white coloration.

According to this question, a white bull (rr) is crossed with a white cow (rr). Each parent will produce the "r" gamete, which when used in a punnet square will produce all WHITE COWS i.e 100% white cows. See punnet square attached.

answer; i believe that the correct answer is(d) nondisjunction during meiosis;

i think that it is plants