Notes: Mendel’s Law of
Independent Assortment
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Mendel wondered if genes that determined different traits affected one another (example: does
pea color affect the shape of the pea?).
• Mendel found that the genes for pea color did not affect how the gene for pea shape sorted.
Mendel’s Law of Independent Assortment
states that allele pairs separate independently during the formation of gametes. This means that
traits are transmitted to offspring independently of one another.
Mendel proved this with the Dihybrid Cross (two traits)
P Generation Cross
RRYY
x
rryy
Round/Yellow
wrinkled/green
F1 Generation self-fertilizes
RrYy x RrYy
F2 Genotypes
1 RRYY
2 RRYy
2 RrYY
4 RrYy
F2Phenotypes
9
Round Yellow
1 Rryy
2 Rryy
3
Round green
1 rrYY
2 rrYy
3
wrinkled Yellow
1
1 rryy wrinkled green
REMEMBER: All dihybrid crosses with both parents heterozygous for the trait result in a
9:3:3:1 phenotypic ratio. All monohybrid crosses with both parents heterozygous for the trait
result in a 3:1 phenotypic ratio.