A dominant gene \"A\" governs the production of purple anthocyanin pigment in to
ID: 324426 • Letter: A
Question
A dominant gene "A" governs the production of purple anthocyanin pigment in tomato stems and its recessive allele "a" produces green stem. A dominant gene "HI" controls the development of hairy stems and its recessive allele "hl" produces hairless stems. A dihybrid purple, hairy plant is test crossed and produces: 73 purple, hairy 12 purple, hairless 75 green, hairless 9 green, hairy Is the purple: green ratio among the test cross progeny compatible with the expectation for segregation? Support your answer using Chi-square analysis.Explanation / Answer
If these genes are showing mendilian inheritance, the test cross ration shoud be in 1:1:1:1 ratio.
Chisquare analysis
Null hypothesis : The observed values are not deviating from the 1:1:1:1 ratio
Category
purple hairy
purple hairless
green hariless
green hairy
Total
Observed values
73
12
75
9
169
Exptected Ratio
1
1
1
1
4
Exprected Values
42.25
42.25
42.25
42.25
Deviation
30.75
-30.25
32.75
-33.25
D^2
945.5625
915.0625
1072.563
1105.563
D^2/E
22.38018
21.65828
25.38609
26.16716
95.59172
X^2
95.59172
Degrees of freedom
4-1 = 3
Inference: The calculated chi square value is greater than the table value i.e. 7.82 at 3 DF and 0.05 probability. Hence Null hypothesis is rejected. Those genes are not showing mendilian inheritance which means those are not showing indipendent assortment.
Category
purple hairy
purple hairless
green hariless
green hairy
Total
Observed values
73
12
75
9
169
Exptected Ratio
1
1
1
1
4
Exprected Values
42.25
42.25
42.25
42.25
Deviation
30.75
-30.25
32.75
-33.25
D^2
945.5625
915.0625
1072.563
1105.563
D^2/E
22.38018
21.65828
25.38609
26.16716
95.59172
X^2
95.59172
Degrees of freedom
4-1 = 3
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