Pure pea plants with purple flowers are mated with pure peas with white flowers. All of the F1 have purple flowers. The F1 are crossed and the flower-color of 628 offspring are analyzed.

Question

What are the expected numbers of offspring of each type? Note: Round to the nearest whole number.

Calculate the chi-square statistic (to 2 places after the decimal) for the cross in problem (1) if the F2 were 505 purple and 113 white.

Answer 1

Hi Rebecca,

I don't know if you still need an answer but here is the way that I worked out your problem. Unfortunately, I'm unable to draw the Chi-square so you'll just have to draw it yourself.

1. According to your problem, all F1 flowers were purple. The genetic code would be Pw.
2. The F1 generation would have the following genetic ratio: 3 purple flowers (1 PP and 2 Pw)

P w 1 white flower (ww)

P PP Pw

w Pw ww

3 There is a 3:1 ratio of purple flowers to white flowers. So, 1/4 of the flowers are white while 3/4 are

purple.

4 What is 1/4 of 628 F1 generation flowers. Equation would be 1 x 628 = 628 = 157 white flowers

4 x 1 4

5 To find the number of purple flowers, set up another equation: 157 x 3 = 471 purple flowers.

6 Check your answer by adding: 157 white flowers + 471 purple flowers = 628 F1 flowers.