Use the following data to answer questions 68 A dihybrid tes

Use the following data to answer questions 6-8. A dihybrid test cross is made between the genes C and D with the following results: Calculate the x^2 value used test the hypothesis that the C and D genes are unlinked. 0 0.0576 10.8 14.4 Cannot be determined How many degrees of freedom are there? 1 2 3 4 Given this data, which of the following is the most accurate range within which the p value falls, and what can be concluded? 0

Solution

1. Answer 14.4

Calculate. frequency of 4 alleles

Step 2 : Calculate the expected numbers

CD = 0.502*0.502*1000 = 252                Cd = 0.502*0.498*1000=250

cD = 0.498 * 0.498 * 1000=248               cD = 0.498*0.502*1000=250

Step 3 :Fitness table

2. The degree of freedom is 1. Due to 4 categories we lost has n-1=3. Further we use to calculate expected frequency from C and D alleles, so we have subtract further 2 from 3.

3. Refer the chi square table and see in the Degree of freedom=1. The critical value for p=0.01 is 6.635. Therefore, since our test statistic value exceeds 6.635, p<0.01. This indicates that we should reject the hypothesis that the alleles of the C and D genes are linked.

Test cross	Observed	Expected	Observed-Expected	(Obs-Exp)2 / Exp
CD	222	252	-30	3.57
cd	218	248	-30	3.62
Cd	280	250	30	3.60
cD	280	250	30	3.60
Total				14.4