Two pea plants with purple flowers are crossed Among the off

Two pea plants with purple flowers are crossed. Among the offspring, 63 have purple flowers, and 17 have white flowers. With a chi-square test, compare the observed numbers with a 3:1 expected ratio and determine the probability that the difference between observed and expected could be a result of chance. Enter the appropriate numbers in the blanks provided. For answers requiring numbers, use two significant figures.

(a) chi square value ____

(b) degrees of freedom ____

(c) Are the results due to chance? Enter yes or no. ____

Solution

Lets calculate the chi square take the value of numbers into the chi-square equation: (63 – 60)2/60 + (17 – 20)2 /20 = 0.15 + 0.45 = 0.6 (the chi-square statistic).

Degrees of freedom = the number of classes (phenotypes) – 1 = 2 – 1 = 1.

At one degree of freedom and value of 5%, we do not reject the hypothesis and thus the differences are a result of chance. We can further conclude that both purple parents are heterozygous at the single gene locus controlling flower color (at least for purple and white).