Question

Cross 1: wildtype x white eyes/yellow bodies Fi: Females- 80 wildtype Males- 121 white eyes/yellow bodies The Fı generation is selfed producing: F2: wildtype White eyes/yellow bodies Wildtype eyes/yellow bodies White eyes/wildtype bodies Females 164 101 Males 132 109 3 How can I produce a chi-square test to test if the genes are sex linked and non-linked?

Answer 1

Here,

H₀ : Here gens are not sex - linked.

H_a : Here genes are pro - sex - linked.

Here observed Table is

	Females	Males	Total
WT	164	132	296
WE/YB	101	109	210
WE/YB	2	3	5
WTE/WTB	8	5	13
Total	275	249	524

Now expected taable is

Expected value for each cell is calculated by i.e.

Wildtype female Expected value = Total females * total wildtype only /total number of people = 275 * 296/524 = 155.34

WIldtype Male Expected value = Total males * total wildtype only /total number of people = 249 * 296/524 = 140.66

SO observed table is

	Females	Males	Total
WT	155.34	140.66	296
WE/YB	110.21	99.79	210
WE/YB	2.62	2.38	5
WTE/WTB	6.82	6.18	13
Total	275	249	524

Now Value of Chi-square X²   = Σ(O_i - E_i)²/E_i

	Females	Males	Total
WT	0.48	0.53	1.02
WE/YB	0.77	0.85	1.62
WE/YB	0.15	0.16	0.31
WTE/WTB	0.20	0.22	0.43
Total	1.60	1.77	3.37

Here X² = 3.37

Degree of freedom = (2 -1) * (4 - 1) = 3

alpha = 0.05

X²_critical = 7.8147

p - value = 0.3374 > 0.05

So we fail to reject the null hypothesis and can say that the genes are not sex linked.