how to do chi-square calculations on this? 2. The following are dihybrid F2 data
ID: 199956 • Letter: H
Question
how to do chi-square calculations on this?
2. The following are dihybrid F2 data. Do these data support the hypothesis of independent assortment? Complete the table, calculate X2, and answer the questions based on your calculations Phenotype (O-E) (O-E) O-EHE A B 406 A bb 149 162 51 Total A. In interpreting this X2 value, you have degrees of freedom. B. In this case do you accept/reject the hypothesis that these data approximate the dihybrid F ratio with independent assortment? C. What is the probability that the deviations are due to chance alone? D. Complete the following table for the data given. Determine whether each gene pair is behaving according to Mendel's first law, giving a 3:1 ratio. Note that because F2 data are being considered in this problem, one might reasonably expect each individual trait to behave according to Mendels law of segregation, giving a 3:1 ratio. Accept or reject X2 value P value hypothesis Hypothesis 3 A-: I aa 3 B-: 1 bbExplanation / Answer
Null hypothesis : The observed values are not deviating from the 9:3:3:1 ratio.
Test Static – chisquare test:
Category
A_B_
A_bb
aaB_
aabb
Total
Observed values (O)
406
149
162
51
768
Exptected Ratio (ER)
9
3
3
1
16
Exprected Values (E)
432
144
144
48
Deviation (O-E)
-26
5
18
3
D^2
676
25
324
9
D^2/E
1.564815
0.173611
2.25
0.1875
4.175926
X^2
4.175926
Degrees of freedom
4
-
1
3
Inference: The calculated chisquare value i.e. 4.17 is less than the table value i.e. 7.82 at 3 DF and 0.05 probability. Hence the null hypothesis is accepted. Which means the observed values fit to 9:3:3:1 ratio.
a. 3 DF, Degrees of freedom = no. of categories; 4-1 = 3
b. Accepted because the calculated chisquare value i.e. 4.17 is less than the table value i.e. 7.82 at 3 DF and 0.05 probability
d. After arranging the data as per alleles:
For allele A:
A _ : 406+149 : 555
Aa : 162+ 51 : 213
Null hypothesis : The observed values are not deviating from the 3:1 ratio.
Category
A_
aa
Total
Observed values
555
213
768
Exptected Ratio
3
1
4
Exprected Values
576
192
Deviation
-21
21
D^2
441
441
D^2/E
0.765625
2.296875
3.0625
X^2
3.06
Degrees of freedom
-
1
Inference: The calculated chisquare value i.e 3.06 is less than the table value i.e. 3.84 at 1 DF and 0.05 probability. Hence the null hypothesis is accepted. Which means the observed values fit to 3:1 ratio.
For allele B:
B_ : 406+162 = 568
Bb : 149+51 = 200
Null hypothesis : The observed values are not deviating from the 3:1 ratio.
Category
B_
bb
Total
Observed values
568
200
768
Exptected Ratio
3
1
4
Exprected Values
576
192
Deviation
-8
8
D^2
64
64
D^2/E
0.111111
0.333333
0.444444
X^2
0.44
Degrees of freedom
-
1
Inference: The calculated chisquare value i.e 0.44 is less than the table value i.e. 3.84 at 1 DF and 0.05 probability. Hence the null hypothesis is accepted. Which means the observed values fit to 3:1 ratio.
Category
A_B_
A_bb
aaB_
aabb
Total
Observed values (O)
406
149
162
51
768
Exptected Ratio (ER)
9
3
3
1
16
Exprected Values (E)
432
144
144
48
Deviation (O-E)
-26
5
18
3
D^2
676
25
324
9
D^2/E
1.564815
0.173611
2.25
0.1875
4.175926
X^2
4.175926
Degrees of freedom
4
-
1
3
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.