(Problem 17) Perform a chi-square test of independence on the data provided in F

Question

(Problem 17) Perform a chi-square test of independence on the data provided in Figure 5.2 to determine if the F2 are segregating in a 9:3:3:1 ratio. How many degree(s) of freedom should be used to determine if the genes are assorting independently?

A. 1

B. 2

C. 3

D. 4

Experiment Question: Do the genes for flower color and pollen shape in sweet peas assort independently? Cross two strains homozygous for two different traits. Methods P generation Homozygous strains Purple flowers, Red flowers long pollen round pollen O Pollen F, generation Purple flowers long pollen Self-fertilization Results F: generation Purple PurpleRed Red 24 Ppe oweround flowers,flowers flowers, flowers, long roundlong round pollen pollen pollen pollen 21 21 Conclusion: F2 progeny do not appear in the 9:313:1 ratio expected with independent assortment. Figure 5.2 Genetics Essentials: Concepts and Connections, Third Edition 2016 Macmilan Education

Explanation / Answer

Answer : C. 3

Degree of freedom is basically known as an estimate of the number of independent categories in a particular statistical test or experiment. And it is denoted by df. And the formula for finding the degree of freedom is:. n - 1 where n is the number of classes for example in the first figure there are 4 different classes namely purple flower, red flower, long pollen and round pollen so there are four different classes. So degree(s) of freedom that should be used to determine if the genes are assorting independently will be calculated as follows: df= n - 1

= 4 - 1 ( n= 4 which means number of classes)

df = 3

So the degree of freedom is 3.

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