Independent Assortment and Gamete
Formation in a Dihybrid Cross
• Example
– Parents
• 1: round yellow peas
(RRYY)
• 2: wrinkled green peas
(rryy)
F1 Dihybrid crosses
One Parent r
• F1:
• Genotype Ratio
• Phenotype Ratio
r y y Second Parent R R Y Y
• Parents
• 1: round yellow peas (RRYY)
• 2: wrinkled green peas (rryy)
Dihybrid crosses
• F1: All round, yellow peas
• Genotype Ratio
• Phenotype Ratio
16:0
16:0
rryy
ry
ry
ry
ry
RY
RrYy
RrYy
RrYy
RrYy
RY
RrYy
RrYy
RrYy
RrYy
RY
RrYy
RrYy
RrYy
RrYy
RY
RrYy
RrYy
RrYy
RrYy
F Dihybrid crosses
Traits for the alleles
Dominant: Round/Yellow
Recessive: wrinkled/green
Fill in the punnett square
with the genotype for each
possible offspring (gamete/
sex cell)
Genotype Ratio
RrYy
Rr Yy
2
F Dihybrid crosses
•
•
Dominant: Round/Yellow
Recessive: wrinkled/green
• F2 Genotype Ratio
2
1:2:2:4:2:2:1
RrYy
RY
RrYy
Ry
rY
ry
RY
RRYY
RRYy
RrYY
RrYy
Ry
RRYy
RRyy
RrYy
Rryy
rY
RrYY
RrYy
rrYY
rrYy
ry
RrYy
Rryy
rrYy
rryy
F Dihybrid crosses
Traits for the alleles
Dominant: Round/Yellow
Recessive: wrinkled/green
Fill in the punnett square
with the phenotype for
each possible offspring
(gamete/sex cell)
Phenotype Ratio
RrYy
Rr Yy
2
F Dihybrid crosses
•
•
Dominant: Round/Yellow
Recessive: wrinkled/green
• F2 Phenotype Ratio
2
9:3:3:1
RrYy
RY
RrYy
Ry
rY
ry
RY
Round
Yellow
Round
Yellow
Round
Yellow
Round
Yellow
Ry
Round
Yellow
Round
green
Round
Yellow
Round
green
rY
Round
Yellow
Round
Yellow
wrinkled Yellow
wrinkled Yellow
ry
Round
Yellow
Round
green
wrinkled Yellow
wrinkled green