What is the ratio of phenotypes in the offspring produced by the cross Aa x Aa, assuming complete dominance for the trait?
a. 100% dominant (D)
b. 100% recessive (R)
c. 25% D, 75% R
d. 50% D, 50% R
e. 75% D, 25% R
One gets AA, Aa, aA, aa so three of the four has a dominate A.
To determine the ratio of phenotypes in the offspring of a cross, we need to consider the possible combinations of alleles from the parents. In this case, both parents are heterozygous (Aa) and the trait exhibits complete dominance.
When crossing Aa x Aa, there are four possible combinations of alleles that the offspring can inherit from the parents: AA, Aa, aA, and aa. Here, the capital letter represents the dominant allele, and the lowercase letter represents the recessive allele.
Out of the four possible combinations, three involve the dominant allele A (AA, Aa, aA). Therefore, the ratio of dominant phenotypes (D) to recessive phenotypes (R) will be 3:1.
So, the correct answer is c. 25% D, 75% R.