In all cells with initial values you can put data, leave the zeros in the empty fields
The number of degrees of freedom for the Chi-square is equal to 1, 4 and 2 for the three possible combinations 2 by 2, 3 by 3 or 2 by 3 table.
- Put your observed numbers and click the Calculate button.
AB gametes 10 Ab gametes 20 aB gametes 20 ab gametes 10
The numbers are given in the initial values of the program. Factor 1 is corresponding
to locus A and Factor 2 is corresponding to locus B. Press the
Calculate button to see the result.
The Chi-square are equal to 6.66 (df=1) which is
larger then 3.84, this means that there is less than 5% chance that the genes at the
two loci segregate independently.
Genotype Observed numbers
Diseased Healthy
AA 15 27
Aa 16 28
aa 51 49
Is there statistically significant association between genotype and disease frequency ?
The two dominant genotypes can be merged into one with the following results:
Genotype Observed numbers
Diseased Healthy
A- 31 55
aa 51 49
What can justify to merge the to classes into one? Is there now statistically significant association between genotype and disease frequency ?
In a two gene system you have the following set of observed numbers:
Genotype BB Bb bb
----------------------------
AA | 57 140 101
Aa | 39 224 226
aa | 3 54 156
Are there statistically significant association between the segregating
genes at the to loci ?
In case there is found association, what does this mean ?
Can you propose a chi-square test which give 6 degrees of freedom
to test a hypothesis of linkage between the genes A and B ?
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