Use the figure and the following description to answer the question.
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding, dark-leaved plant is crossed with a light-leaved one, and the F₁ offspring is allowed to self-pollinate. The predicted outcome of the F₂ is diagrammed in the Punnett square shown in the figure, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.

Which of the boxes marked 1-4 correspond to plants with a heterozygous genotype?
A) 1
B) 1, 2, and 3
C) 2 and 3
D) 2, 3, and 4

Question

Use the figure and the following description to answer the question.
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding, dark-leaved plant is crossed with a light-leaved one, and the F₁ offspring is allowed to self-pollinate. The predicted outcome of the F₂ is diagrammed in the Punnett square shown in the figure, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.

Which of the boxes marked 1-4 correspond to plants with a heterozygous genotype?
A) 1 
B) 1, 2, and 3 
C) 2 and 3 
D) 2, 3, and 4

Quizplus · Accepted Answer

A heterozygous genotype would mean that the plant has one dominant allele and one recessive allele. In this Punnett square, boxes 2 and 3 correspond to the heterozygous genotypes (Dd) because they have one uppercase D allele and one lowercase d allele. Box 1 is homozygous dominant (DD) and box 4 is homozygous recessive (dd). Therefore, the best choice is C, which includes boxes 2 and 3.

Use the Figure and the Following Description to Answer the Question