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conduct a chi square analysis to determine if these two genes are linked. if the

ID: 88756 • Letter: C

Question


conduct a chi square analysis to determine if these two genes are linked. if they are linked, calculate the map distance between the two genes.

factor cross was by crossing a plant with yellow pods and curling leaves to a wild-type made plant with green pods and normal leaves. All the Fi offspring had green pods and normal leaves. The F1 plants were then crossed to plants with yellow pods and curling leaves. The following results were obtained: 17 green pods, normal leaves 115 yellow pods, curling leaves 78 green pods, curling leaves 80 yellow pods, normal leaves A. Conduct a Chi-Square analysis to determine if these two genes are linked. B. If they are linked, calculate the map distance between the two genes.

Explanation / Answer

Part A)

Null hypothesis : The observed values are not deviating from 1:1:1:1 ratio.

Category

Green, Normal

Yellow, curling

green, curling

yellow, normal

Total

Observed values

117

115

78

80

390

Exptected Ratio

1

1

1

1

4

Exprected Values

97.5

97.5

97.5

97.5

Deviation

19.5

17.5

-19.5

-17.5

D^2

380.25

306.25

380.25

306.25

D^2/E

3.9

3.141026

3.9

3.141026

14.08205

X^2

14.08205

Degrees of freedom

4-1 = 3

Inference: The calculated chisquare value i.e.14.08 is higher than the table value i.e. 7.82 at 0.05 probability and 3 DF. Hence null hypothesis is rejected. Which indicates that the gene are linked.

Part B)

The map distance between genes = (Total frequency of recombinants / Total no of progeny) X 100

= (78+80 / 117+115+78+80) X 100 = (158/ 390) X 100 = 40.51

Category

Green, Normal

Yellow, curling

green, curling

yellow, normal

Total

Observed values

117

115

78

80

390

Exptected Ratio

1

1

1

1

4

Exprected Values

97.5

97.5

97.5

97.5

Deviation

19.5

17.5

-19.5

-17.5

D^2

380.25

306.25

380.25

306.25

D^2/E

3.9

3.141026

3.9

3.141026

14.08205

X^2

14.08205

Degrees of freedom

4-1 = 3