. You have two true-breeding tomato plants. One is tall (T) with a bristly stem
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Question
. You have two true-breeding tomato plants. One is tall (T) with a bristly stem (B) and white flowers (r). The other is short (t) with a smooth stem (b) and red flowers (R). These plants are crossed, producing a heterozygous F1 generation that is tall with bristly stems and red flowers. You predict that self-fertilization of the F1 generation will result in offspring that inherit their alleles in a manner consistent with simple Mendelian inheritance.
You grow 900 F2 tomato plants and record the following results:
412 Tall bristly plants with red flowers
115 Tall smooth plants with red flowers
130 short bristly plants with red flowers
98 tall bristly plants with white flowers
40 short smooth plants with red flowers
56 tall smooth plants with white flowers
37 short bristly plants with white flowers
12 short smooth plants with white flowers
a. What is the expected number for each phenotype if your hypothesis is correct?
b. How many degrees of freedom are there?
c. Is the hypothesis supported or rejected? Why?
Explanation / Answer
. You have two true-breeding tomato plants.
One is tall (T) with a bristly stem (B) and white flowers (r).
The other is short (t) with a smooth stem (b) and red flowers (R).
TTBBrr x ttbbRR
TtBbRr X TtBbRr
TBR; TBr; TbR ; Tbr;
tBR, tBr, tbR; tbr
gametes
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
You grow 900 F2 tomato plants and record the following results:
412 Tall bristly plants with red flowers
115 Tall smooth plants with red flowers
130 short bristly plants with red flowers
98 tall bristly plants with white flowers
40 short smooth plants with red flowers
56 tall smooth plants with white flowers
37 short bristly plants with white flowers
12 short smooth plants with white flowers
PHENOTYPE RATIO 27:9:9:9:3:3:3:1
GENOTYPE phenotype
OBSERVED
EXPECTED
O-E
(O-E)^2
(O-E)^2/E
Tall bristly plants with red flowers
412
378
34
1156
3.05
Tall smooth plants with red flowers
115
126
-11
121
0.96
short bristly plants with red flowers
130
126
4
16
0.12
tall bristly plants with white flowers
98
126
-28
784
6.2
short smooth plants with red flowers
40
42
-2
4
0.09
tall smooth plants with white flowers
56
42
-14
196
4.6
short bristly plants with white flowers
37
42
-5
25
0.57
short smooth plants with white flowers
12
14
-2
4
0.28
Total
900
CHI-SUARE VALUE= (O-E)^2/E
NULL hypothesis: THE OFFSPRING ARE ACCORDING TO HARDY WEINBERG LAW
ALTERNATIVE hypothesis: THE OFFSPRING ARE NOT ACCORODING TO HARDY WEINBERG LAW
CALCULATE VALUE IS MORE THAN TABLE TABLE AT 5% LEVEL OF SIGNIFICANCE , HENCE REJECT THE NULL hypothesis AND ACEPT
ALTERNATIVE hypothesis.
gametes
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
TBR
TBR
TBr
TbR
Tbr
tBR,
tBr
tbR
tbr
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