Chi-Squared TestMendelian Genetics

Purpose A test used to determine if real data

matches what the ratios a Punnett square predicts

Example Question In a dihybrid inheritance problem, you have

a chi-squared value of 10.25 with a degree of freedom (df) 3. Does this organism match the ratios predicted in the dihybrid cross?

Example Question In a dihybrid inheritance problem, you have

a chi-squared value of 1.3 with a degree of freedom (df) 3. Does this organism match the ratios predicted in the dihybrid cross?

Other Types of Inheritance

Pleiotropy

A single gene controls multiple, unrelated alleles Example: Chicken with puffed feathers/also has trouble

with internal body temperature

Multiple Alleles

More than two alleles possible for a single gene

Example: Blood type

Epistasis

Expression of one gene is controlled by the other

Example: Red hair gene and baldness

Polygenetic Inheritance

Many genes contribute to a variety of phenotypes

Example: Skin color, height