Dihybrid Cross (Example Note)
Let R = dom. allele for Round shape
r = rec. allele for Wrinkled shape
Punnett Square
Step 4:
and
Step 1:
RRYY x rryy
Let Y = dom. allele for Yellow colour
y = rec. allele for Green colour
P1
P2
ry
Step 2:
RRYY
pure‐bred
rryy
pure‐bred
RY
RY
RrYy RrYy
RY
RY
RrYy RrYy
ry
F1 Generation
(Possible Genotypes)
ry
RY
Step 3:
RY
RY
ry
RY
Now we can cross 2 members of the F1 (RrYy) generation to do a new dihybrid genetics problem.
P1
RrYy x RrYy
P2
What are the possible gametes?
P1: RrYy RY, Ry, rY, ry
RY
Ry
rY
ry
RY
RRYY RRYy RrYY RrYy
Ry
RRYy RRyy RrYy Rryy
rY
RrYY RrYy rrYY
rrYy
ry
RrYy Rryy rrYy
rrYy
P2: RrYy RY, Ry, rY, ry
F2 Generation
(Possible Genotypes)
F2 Generation
Phenotypic Ratio:
round : round : wrinkled : wrinkled
yellow
green yellow green
9 : 3 : 3 : 1
Phenotypic Ratio: Round Yellow : Round Green : Wrinkled Yellow : Wrinkled Green
dominant for
BOTH traits
dominant for trait 1 recessive for trait 1
recessive for trait 2 dominant for trait 2
recessive for BOTH traits
1