What ratio of the offspring from the cross shown above will be homozygous recessive for the trait of round seed shape?

A. 0 in 4
Correct! Homozygous recessive traits are indicated with lowercase letters and would be rr.

B. 1 in 4
Incorrect. Homozygous recessive traits are indicated with lowercase letters.

C. 2 in 4
Incorrect. Homozygous recessive traits are indicated with lowercase letters.

D. 4 in 4
Incorrect. Homozygous recessive traits are indicated with lowercase letters.

In a certain variety of plant, red flower color is completely dominant to white flower color, r. If the plant is heterozygous for flower color, which alleles will be carried by the gametes it produces?

A. R and r
Correct! A heterozygous plant would have one dominant allele and one recessive allele.

B. R only
Incorrect. Having two alleles of the same type indicates a homozygous individual.

C. r only
Incorrect. Having two alleles of the same type indicates a homozygous individual.

D. Rr only
Incorrect. According to the law of segregation, a gamete has only one copy of an allele.

In squash plants, yellow fruit (Y) is dominant to white fruit (y). If two plants heterozygous for yellow fruit are crossed, what are the possible genotypes of the offspring?

A. Yy only
Incorrect. For this to be possible, one parent would have to be homozygous dominant and the other would have to be homozygous recessive.

B. YY, yy only
Incorrect. This combination is not possible.

C. Yy, yy only
Incorrect. For this to be possible, one parent would have to be a heterozygote and one would have to be homozygous recessive.

D. YY, Yy, yy only
Correct! Heterozygote parents produce all of the possible combinations of alleles.

What do the letters on the outside (top and side) of a Punnett square represent?

A. The possible genotypes of the female offspring
Incorrect. The possible genotypes of the offspring are in the center boxes of the Punnett square.

B. The possible genes carried by gametes of the parents
Correct!

C. The possible genotypes of the male offspring
Incorrect. The possible genotypes of the offspring are in the center boxes of the Punnett square.

D. The dominant traits are on the outside top and the recessive traits are on the outside left side of a Punnett square.
Incorrect. The possible genes carried by gametes of the parents are placed on the outside of the Punnett square.

Which of the following Punnett squares correctly shows the crosses between a homozygous dominant purple flower and white flower? (Purple flower color is the dominant allele.)

A.
Incorrect. This Punnett square shows the cross between two plants that are heterozygous for flower color.

B.

Incorrect. This Punnett square shows the cross between a homozygous recessive and a heterozygous plant for flower color.

C.

Incorrect. This Punnett square shows the cross for two homozygous recessive plants for flower color.

D.

Correct!