1. Chi Square in IB Biology 10.2 part 2

2. In this class it will be either testing to see if organisms are randomly distributed (ecology) or to see if genes are linked or not (genetics)

3. Degrees of freedom: The number of groups -1
For our problems this will most likely be the number of phenotypes possible -1
If X2 value falls to the right of the 0.05 column we reject our null hypotheses that the genes are not linked

4. CORN GENETICS CHI SQUARE ANALYSIS by Biology Corner
10.2.U5 Chi-squared tests are used to determine whether the difference between an observed and expected frequency distribution is statistically significant. AND 10.2.S3 Use of a chi-squared test on data from dihybrid crosses.
Testing dihybrid crosses – using the chi-squared test
Now try extending your understanding of dihybrid crosses using data. Follow the links below and complete the examples and problems:
CORN GENETICS CHI SQUARE ANALYSIS by Biology Corner
Chi-square in biology: Testing for a dihybrid ratio
Answer key:

5. In the species Miceus punkious fangs are a recessive trait (ff) and mohawks are also a recessive trait (mm). Two mice heterozygous for both traits are crossed and the following results are observed:
80 normal mice, 33 fanged, 33 mohawked, and 14 mohawked and fanged. Are these genes linked?

6. Chi square to test if results are close to what was expected
Observed
expected
(o-e)
(o-e)2
(o-e)2/e
Normal 80
Fanged 33
Mohawked
Fanged/mohawked 14
Total
160
     
How many degrees of freedom?

7. Observed
Expected
(o-e)
(o-e)2
(o-e)2/e
Normal 80 90
-10
100
1.11
Fanged 33 30 3 9 .3
Mohawked
Both 14 10 4 16
1.6
Total
160
3.31