In sweet peas, ?owers are typically purple. Plants which are homozygous pp produ

Question

In sweet peas, ?owers are typically purple. Plants which
are homozygous pp produce white ?owers. Plants which are
homozygous cc also produce white ?owers. In a cross of
CC pp x cc P P , the F1 are all purple. When the F1 is selfed,
the resulting F2 is 9/16 purple and 7/16 white.

7. [2pt] What is the probability that a randomly chosen F2
purple plant will breed true? Express your answer as a decimal
fraction with 4 signi?cant digits (e.g. 0.1234)

Explanation / Answer

P1 Generation: CCpp x ccPP Gamete produced from CCpp genotype --> Cp Gamete produced from ccPP genotype --> cP F1 Generation: CcPp (all purple) F1 x F1: CcPp x CcPp You can consider this cross as two seperate monohybrid crosses: Cc x Cc and Pp x Pp The genotypic probabilities for each of the crosses would be as follows: 1/4 CC, 2/4 Cc, and 1/4 cc 1/4 PP, 2/4 Pp, and 1/4 pp The question is asking for the probability that a random chosen plant will breed true. This basically means you have to take into consideration the homozygous dominant genotypes and NOT the homozygous recessive genotypes. This is because homozygous recessive gives the white trait and not the purple one. 1/4 CC x 1/4 PP = 1/16 CCPP The answer is 1/16 = 0.0625 Hope this helps! :-)

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