Genetics Dihybrid Crosses

​Dihybrid Crosses

What is a dihybrid cross?

*A dihybrid cross is a cross among two
traits.

DI= TWO
HYBRID=

COMBINATION

Dihybrid Punnett squares are
prediction tools used to determine
probability for two traits.

Problem: Show the possible genetic

combinations among offspring of a man who

is heterozygous for both dimples and

freckles, and a woman who is recessive for

dimples and freckles.

​FfDd x ffdd

Setting up a dihybrid cross

When setting up your dihybrid

cross, you first need to

determine possible combinations

among alleles for each gene

when forming gametes.

Remember, you only inherit one
allele per gene from each parent.

When setting up a
dihybrid Punnett

Square, we can use

the FOIL method.

FfDd x ffdd

FD

Fd

fD

fd

*Foil Method FfDd

(F f) (D d)

FIRST (of each letter) = FD

OUTSIDE = Fd

INSIDE = fD

LAST (of each letter) = fd

Setting a dihybrid cross

FfDd x ffdd

Which percentage of offspring

can be predicted to have

freckles (F) AND dimples (D)?

4 out of 16 or 25%

Which percentage of offspring

can be predicted to have

freckles (F) but NO dimples (d)?

4 out of 16 or 25%

Which percentage of offspring

can be predicted to have

dimples (D) but NO freckles (f)?

4 out of 16 or 25%

Which percentage of offspring
can be predicted to have no
freckles (f) nor dimples (d)?

4 out of 16 or 25%

In cats, short tails are dominant (S)

and brown fur is dominant (B).
Cross two heterozygous cats.

What will the offspring look like?

Short Tails & Brown Fur: _______%
Short Tails & White Fur: _______%
Long Tails & Brown Fur: _______%
Long Tails & White Fur: _______%

______________ x ______________

F

O

I

L

In cats, short tails are dominant (S)

and brown fur is dominant (B).
Cross two heterozygous cats.

What will the offspring look like?

Short Tails & Brown Fur: _______%
Short Tails & White Fur: _______%
Long Tails & Brown Fur: _______%
Long Tails & White Fur: _______%

______________ x ______________

F

O

I

L

​SsBb

​SsBb

In cats, short tails are dominant (S)

and brown fur is dominant (B).
Cross two heterozygous cats.

What will the offspring look like?

Short Tails & Brown Fur: _______%
Short Tails & White Fur: _______%
Long Tails & Brown Fur: _______%
Long Tails & White Fur: _______%

______________ x ______________

F

O

I

L

​SsBb

​SsBb

​SB

​SB

​Sb

​Sb

​sB

​sB

​sb

​sb

Multiple Choice

In cats, short tails are dominant (S) and brown fur is dominant (B). Cross two heterozygous cats. What will the offspring look like?

• 4 Short Tails Brown Fur

  4 Short Tails White Fur

  4 Long Tails Brown Fur

  4 Long Tails White Fur

• 8 Short Tails Brown Fur

  4 Short Tails White Fur

  4 Long Tails Brown Fur

  0 Long Tails White Fur

• 9 Short Tails Brown Fur

  3 Short Tails White Fur

  3 Long Tails Brown Fur

  1 Long Tails White Fur

• 4 Short Tails Brown Fur

  4 Short Tails White Fur

  4 Long Tails Brown Fur

  4 Long Tails White Fur

Patterns in Dihybrid Crosses

*A similar pattern can be found
when creating a dihybrid cross
among two individuals who are
heterozygous for both traits.

Example) Crossing two short-tailed

brown cats that are both heterozygous

for each trait.

Short tails are dominant (S); Brown fur

is dominant (B)

9 Short-tailed Brown cats

3 Short-tailed white cats

3 long-tailed Brown cats

1 long-tailed white cats

Patterns

Recall that specific statistics were seen in Mendelian genetics
when crossing two heterozygous individuals in monohybrid
crosses.
3:1 Dominant: Recessive
1: 2: 1 Homozygous Dominant: Heterozygous: Homozygous Recessive

Mendel repeated his

experiment many
times, and always
obtained the same

results in the F2

generation.