If ABAB is crossed with abab and the F1 is testcrossed the f

If AB/AB is crossed with ab/ab and the F1 is testcrossed, the figure below depicts two sets of data obtained from testcross experiments asking whether genes A and B are linked. Are A and B genes linked in experiment #2 if the Chi square value of the experiment is calculated to be 5.76? Show me data interpretation to earn full credit.

Solution

Accroding to your work book the chisquare test summary for expriment is

Null hypothesis: The observed values are not deviating form the Expected 1:1:1:1 ratio.

Category

AB + ab

Ab + aB

Total

Observed values

62

38

100

Exptected Ratio

1

1

2

Exprected Values

50

50

Deviation

12

-12

D^2

144

144

D^2/E

2.88

2.88

5.76

X^2

5.76

Degrees of freedom

2-1

1

Inference: The calculated chi square value is lessthan the table value @ 1 DF and 0.05 probability i.e. 3.841, Hence null hypothesis rejected.

But, while calculting the chisquare test you shuold not merge the catergories. The data is not showing any linkage information. If you merge the categories it is showing that those genes are linked. But if you follow the actual process it is giving the support to orignial raw data. Just do discuss about this with your masters in Genetics and comment me if you need any help.

The actual process to calculte the chisquare test :

For experiment I:

Null hypothesis: The observed values are not deviating form the Expected 1:1:1:1 ratio.

Category

AB

ab

Ab

aB

Total

Observed values

17

14

8

11

50

Exptected Ratio

1

1

1

1

4

Exprected Values

12.5

12.5

12.5

12.5

Deviation

4.5

1.5

-4.5

-1.5

D^2

20.25

2.25

20.25

2.25

D^2/E

1.62

0.18

1.62

0.18

3.6

X^2

3.6

Degrees of freedom

4-1 = 3

Inference: The calculated chi square value is lessthan the table value @ 3 DF and 0.05 probability i.e. 7.815, Hence null hypothesis accepted.

For experiment II:

Null hypothesis: The observed values are not deviating form the Expected 1:1:1:1 ratio.

Category

AB

ab

Ab

aB

Total

Observed values

34

28

16

22

100

Exptected Ratio

1

1

1

1

4

Exprected Values

25

25

25

25

Deviation

9

3

-9

-3

D^2

81

9

81

9

D^2/E

3.24

0.36

3.24

0.36

7.2

X^2

7.2

Degrees of freedom

4-1

3

Inference: The calculated chi square value is lessthan the table value @ 3 DF and 0.05 probability i.e. 7.815, Hence null hypothesis accepted.

Category	AB + ab	Ab + aB	Total
Observed values	62	38	100
Exptected Ratio	1	1	2
Exprected Values	50	50
Deviation	12	-12
D^2	144	144
D^2/E	2.88	2.88	5.76
X^2	5.76
Degrees of freedom	2-1	1