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. white flowers and purple flowers are codominant.
b. purple flowers are dominant to white flowers.
c. purple flowers and white flowers are recessive to red.
d. white flowers are dominant to purple flowers.

Explanation:

• For option A: Codominance would result in a phenotype that shows both traits (e.g., a mix of white and purple), but the offspring here are all purple, so A is incorrect.
• For option B: When a homozygous purple flower (let's say PP) and a homozygous white flower (pp) are crossed, the offspring will have the genotype Pp. If all offspring show the purple phenotype, that means the purple allele is dominant over the white allele, so B is correct.
• For option C: There is no mention of a red flower trait in the experiment, so C is incorrect.
• For option D: The offspring are all purple, not white, so white cannot be dominant over purple, making D incorrect.

Answer:

B. Purple flowers are dominant to white flowers.