genotype and phenotype ratios genetics unit 1

monohybrid cross

geno: 1:2:1 / pheno: 3:1

monohybrid cross for a gene with 2 codominant

phenotypic ratio = genotypic ratio (1:2:1)

how do you know trait A and B are not specified by two difference genes?

test with the 2-gene model with the following cross: AAbb x aaBB

pleiotropy

one gene controls multiple characters because the protein acts differently in different cell types

polymorphic genes

multiple alleles of one gene

epistasis

an allele of one gene masks the effects of alleles at another gene

recessive epistasis

a recessive allele of one gene masks the effects of alleles at another gene

ratio of dihybrid cross with recessive epistasis

9:3:4 (4 has the recessive epistasis gene)

ratio of dihybrid cross of dominant epistasis

12:3:1

reciprocal recessive epistasis (complementary)

being recessive for either one allele or another resulting in the blocking of a different allele

ratio for reciprocal recessive epistasis

9:7

reciprocal dominant epistasis (redundancy)

either allele A or B is sufficient for functional protein

what is the ratio for reciprocal dominant epistasis

15:1