1. Dihybrid crosses

2. Mendel’s Law of Independent Assortment
Mendelian Genetics
4/9/2019
Mendel’s Law of Independent Assortment
Alleles for different traits are distributed to sex cells (& offspring) independently of one another.
This law can be illustrated using dihybrid crosses (breeding experiment that tracks the inheritance of two traits)
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3. Dihybrid Cross RrYy x RrYy Traits: Seed shape & Seed color
Mendelian Genetics
4/9/2019
Dihybrid Cross
Traits: Seed shape & Seed color
Alleles: R round r wrinkled Y yellow y green
RrYy x RrYy
RY Ry rY ry
RY Ry rY ry
The key is to figure out the possible allele combinations for each parent!

4. Dihybrid Cross RY Ry rY ry RY Ry rY ry Mendelian Genetics 4/9/2019
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5. Dihybrid Cross RY Ry rY ry Round/Yellow: 9 Round/green: 3
Mendelian Genetics
4/9/2019
Dihybrid Cross RY Ry rY ry
Round/Yellow: 9
Round/green: 3
wrinkled/Yellow: 3
wrinkled/green: 1
9:3:3:1 phenotypic ratio
RRYY
RRYy
RrYY
RrYy
RRyy
Rryy
rrYY
rrYy
rryy
copyright cmassengale

6. Mendelian Genetics
4/9/2019
Dihybrid Cross
Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1
9:3:3:1
copyright cmassengale

7. NOW…. Practice on your own
NOW…. Practice on your own! Your goal: phenotypic ratios for each dihybrid cross!