How do you test for independent assortment?

Question

How do you test for independent assortment?

How can you tell if genes are assorting independently?

Answer 1

If particular properties are seen going together in a genetic cross i.e. if parental combination exceeds nonparental combination then the genes are linked. If nonparental combination exceeds parental then the genes are not linked i.e. independent assortment.

Answer 2

The actual test you would do is a Chi-squared.  It's a statistical test that tells you the probability that the results you obtained were due only to chance instead of the genes being linked.

For example, if you were doing a cross between two pea plants, both being heterozygous for flower and pod color (PpGg), then you would expect a 9:3:3:1 phenotypic ratio in the offpsring.  But, if you obtained significantly more of two groups than expected (which you would determine with the Chi-squared test), then you would expect that the genes were not assorting independently and were instead linked.

The formula for Chi-squared is ((observed-expected)^2)/expected for each phenotypic class, all summed up together.