Mendel gentics peas

Question

Among the traits that Mendel studied in peas, he determined that the round allele for shape (W) was dominant to the allele for wrinkled (w) peas. Thus, Ww plants produce round peas. You plant 100 plants and after they make pods you look at the peas contained in those pods. From your 100 plants, 25 have wrinkled peas and 75 have round peas. Of those round pea plants, how many do you expect to have a WW genotype? Show your working. (We suggest you either write your Ww’s very legibly or change them to Aa.

Answer 1

Using a monohybrid Punnett Square, the only cross that could produce a 75:25 ratio (3:1 ratio) is Ww x Ww.

Therefore:

1. the chance of WW should be 1:3 or 25%
2. the chance of Ww should be 2:2 or 50%
3. the chance of ww should be 1:3 or 25%

The answer to the question should be 25 are expected to have the genotype WW.

Keep in mind that ratios from Punnett Squares are theoretical predictions. In nature, actual offspring ratios rarely match the expected Punnett square outcomes perfectly due to random variation, especially when sample sizes are small.