Question

Given three possible phenotypes for parents showing dominance (AA, Aa, aa), which combination would produce a 1:2:1 ratio of genotypes and a 3:1 ratio of phenotypes?

I. AA x Aa

II. Aa x aa

III. Heterozygous x Heterozygous

IV. Aa x Aa

V. Homozygous dominant x Heterozygous

Answer 1

it is III and IV
this is correct I took the quiz on usatestprep

Answer 2

Answer: The correct answer is-

III. Heterozygous x Heterozygous and

IV. Aa x Aa.

Genotypic ratio corresponds to the ratio of different genotype produced for the trait ( that depicts the genetic makeup with respect to the trait). On the other hand, phenotypic ratio corresponds to the ratio of phenotypes ( such as tall and dwarf in case of height of pea plant) produced in a generation.

Dominant trait ( depicted by allele with capital letter, such as AA and Aa) masks the expression of recessive trait ( depicted by small letter, such as aa)

Aa and Aa represents heterozygous dominant genotype, which will produce three different genotypes and two different phenotypes in the ratio 1:2:1 and 3:1 respectively.

Refer punnett square.