Chi Square in IB Biology 10.2 part 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)

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

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 http://mathbench.umd.edu/modules/statistical-tests_chisquare_intro/page15.htm http://www.biologycorner.com/worksheets/corn_chi.html Answer key: http://www.biologycorner.com/worksheets/corn_chi_key.html

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?

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?

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