multiple gene inheritance

traits used by Mendel to demonstrate independent assortment

all monogenic and on different chromosomes

dihybrid cross (self)

• result in 4 different phenotypes

• some genotypes produced are unique

• phenotypic ratio of 9:3:3:1

dihybrid testcross for independently assorting genes

• dihybrid testee x homozygous recessive tester

• F1: equal number of parental and recombinant types

• progeny represents meiotic events in dihybrid parent

dihybrid testcross for non-independently assorting genes

• dihybrid testee x homozygous recessive tester

• F1: bias towards parental type, much fewer recombinants

chi-square test

• critical value = sum of [(observed - expected)² / expected] for all phenotypes

• compare critical value to p-value table

• p=0.05 means that there is a 5% chance that hypothesis is true

• p<0.05 means that you can reject the hypothesis with a confidence of 95% or greater

degrees of freedom

number of independent values (ex: phenotypes) - 1