Question

Gregor Mendel crossed true-breeding plants with green pea pods with true-breeding plants with yellow pea pods. The resulting F1 generation all had green pea pods. What did he observe in the F2 generation?
A. Mendel observed green and yellow pea pods in a 3:1 ratio because the F1 generation was heterozygous.
B. Mendel observed green and yellow pea pods in a 4:1 ratio because the allele for green pea pods is dominant.
C. Mendel observed green and yellow pea pods in a 1:1 ratio because the F2 generation had the same characteristics as the parent generation.
D. Mendel observed only green pea pods because both parents had green pea pods.
E. Mendel observed green and yellow pea pods in a 1:2 ratio because the allele for yellow pea pods is dominant.

Answer 1

Answer:

A. Mendel observed green and yellow pea pods in a 3:1 ratio because the F1 generation was heterozygous.

Explanation:

The two true breeding plants in the parental population were homozygous (that is what true breeding means). Therefore, their cross would lead to all heterozygous offspring (see attached punnet square). Green is the dominant characteristic, so all F1 plants had a green phenotype, but Gg genotype.

The F1 cross would therefore be Gg x Gg. See attached punnet square.

The genotypes in the F2 generation are 1 GG: 2 Gg: 1 gg 1

Therefore, the phenotypic ratio is 3 green pea pods (Gg or GG): 1 yellow (gg)

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