Question

3) Write your null hypothesis, perform a chi-square analysis, and answer the questions.

a. Null Hypothesis:

Data	Observed	Expected	O - E	(O – E)2	(O – E)2/E
Round Yellow	910
Round Green	290
Wrinkled Yellow	320
Wrinkled Green	80

b. Degrees of freedom =

c. X² =

d. p =

e. Fail to Reject or Reject null hypothesis?

Answer 1

3) Answer: A χ2 test is done in genetics to check the deviations of observed result from the expected outsomes. The general assumption is that there is no significant deviation between observed and expected values. This assumption is called a null hypothesis. We measure the deviation in terms of chi-square value. If it is high, it means there is significant variation from the result and null hypothesis can be rejected. In lower values, it cannot be rejected. p is the threshold of significance. For a p value < 0.05, the null hypothesis is rejrejecte

A) Null hypothesis
The observed number of progenies in an F2 dihybrid cross is 910,290,320 and 80. But Mendelian ratios refers that the dihybrid ratio is 9:3:3:1 and thus the expected values are 900,300,300 and 100. Thus we can have a null hypothesis that there is no significant deviation between observed and expected values.

B) Degrees of freedom= No. of traits -1
So, 4-1=3

C) Chi-square value= 1.44

D) p can be determined by comparing the crirical value table. By doing so, the p value is in between 0.75-0.50.

E) As the p value is greater than 0.5, there is no significant variation between results. So we fail to reject null hypothesis.