In snapdragons white flowers and short stalk height are inhe

In snapdragons, white flowers and short stalk height are inherited at independent loci and are recessive to their dominant wild-type counterparts, yellow flowers and tall stalk height. Snapdragons that are heterozygous wild-types are crossed, and 9600 progeny are produced.

A. How many progeny are expected to be tall with yellow flowers?

B. How many progeny are expected to be tall with white flowers?

C. How many progeny are expected to be short with yellow flowers?

D. How many progeny flies expected to be short with white flowers?

Solution

Answer:

The wiild type alleles are dominant over ressesive mutant types, as the dominant one hides expression of a ressesive allele. The dominant is represented by an uppercase letter and the mutant one is represented by lowercase letter. In addition, ressesive allele exerts its effect only in the homozygous condition. However in heterozygous condition its expression is hided by a dominant allele.

Thus, as per the given condition in the question:

The crossing of heterozygous wild-types: YyTt (Yellow flower, tall stalk)

F1 generation: YyTt X YyTt

Gametes: 1/4 YT, 1/4 Yt, 1/4 yT, 1/4 yt   1/4 YT, 1/4 Yt, 1/4 yT, 1/4 yt

F2 generation:

Thus, the summary of F2 generation:

Thus, the phenotype in this dihybrid cross gives the results as:  9:3:3:1 ratio.

When 9600 progeny are produced from the above dihybrid cross and the alleles are inherited at independent loci, the number of expected progeny can be calculated using the above observed ratio.

A. The progeny that are expected to be tall with yellow flowers: (9600 X 9)/16 = 5400

B. The progeny that are expected to be tall with white flowers: (9600 X 3)/16 = 1800

C. The progeny that are expected to be short with yellow flowers = (9600 X 3)/16 = 1800

D. The progeny that are expected to be short with white flowers = (9600 X 1)/16 = 600