AP BIOLOGY

HEREDITY

MONOHYBRID CROSS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
In pea plants purple flowers are dominant to white flowers. What parental genotypes would produce offspring that are all homozygous for the purple trait?
A
TT + tt
B
TT + TT
C
tt + tt
D
Tt + Tt
Explanation: 

Detailed explanation-1: -The F1 generation is 100% Pp. The F2 generation is 25% PP (homozygous dominant, purple flowers), 50% Pp (heterozygous, purple flowers), and 25% pp (homozygous recessive, white flowers). This is how the white characteristic reappears in the second generation. The phenotype is 3:1, purple to white.

Detailed explanation-2: -The genotype of purple flowered pea plants is denoted as WW and that of white flowered pea plants as ww.

Detailed explanation-3: -There was a 3:1 ratio of purple:white flowers in generation F2 because the “masked” (recessive) genes from the F1 generation were allowed to pair, however they were only allowed to pair one time leaving the other three times to appear with purple flowers.

Detailed explanation-4: -Answer and Explanation: In this situation, every offspring produced from this cross with be a heterozygote (Pp), and because purple is dominant to white, all the offspring will be purple. Therefore, the probability of an offspring having white flowers is zero.

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