Dihybrid Crosses
Two characteristics at once…• Dihybrid crosses are where we consider heredity
in two characteristics at the same time.• There are four possible combinations of two
characteristics. Example: Pea color and shape. Peas can be...
• 1) round and yellow
• 2) round and green
• 3) wrinkled and yellow
• 4) wrinkled and green
Phenotype Round, yellow Wrinkled, green
Genotype RRYY rryy
Gametes all RY all ry
F1 all RrYy
All in F1 generation are heterozygous for both characteristics (all round and yellow)
X
P generation cross…
Phenotype Round, yellow
Genotype RrYy
Gametes RY, Ry, rY, ry
F2 We really need a punnet square for this…
X Round, yellow
RrYy
RY, Ry, rY, ry
F1 generation cross…
RY Ry rY ry
RY RRYY RRYy RrYY RrYy
Ry RRYy RRyy RrYy Rryy
rY RrYY RrYy rrYY rrYy
ry RrYy Rryy rrYy rryy
F2 generation ratio
9 3 3 1: : :Round
Yellow
Round
Green
Wrinkled
Yellow
Wrinkled
Green
This is the typical ratio expected in an F1 dihybrid
cross
Now for trihybrid Crosses...?
Top Related