Question

Sarah is doing an experiment on pea plants. She is studying the color of the pea plants. Sarah has noticed that many pea plants have purple flowers and many have white flowers. Sarah crosses a homozygous white flower and a homozygous purple flower. The cross results in all purple flowers. What is true of the color of pea plants? A. Purple flowers and white flowers are recessive to red. B. Purple flowers are dominant to white flowers. C. White flowers and purple flowers are codominant. D. White flowers are dominant to purple flowers.

Answer 1

The answer would be b, because every time the flowers would cross over it would result in a purple flower.

Answer 2

Answer:  Option B. Purple flowers are dominant to white flowers.

Explanation:

• Since, Sarah is crossing a homozygous white flower to a homozygous purple flower and yet is getting only purple flower in the progenies it makes it clear that the allele for purple flowers are dominant over white flowers.

• The reason for this is that the recessive alleles are only able to express themselves when they are in homozygous state. Whenever a heterozygous condition occurs the phenotype corresponds to the one encoded by the dominant allele.  

Thus, as the progenies in heterozygous condition are purple, white is recessive in nature.

Refer to the attached diagram to see the cross between the plants.