Punnett Square Practice Worksheet
Part A: Vocabulary - Match the definitions on the left with the terms on the right.
1. genotypes made of the same alleles
A. alleles
2. different forms of genes for a single trait
B. dominant
3. gene that is always expressed
heterozygous
4. gene that is expressed only in the homozygous state
D.
homozygous
5. genotypes made of two different alleles
E. recessive
Circle the choices that are examples of each of those words.
6. Homozygous dominant
AA
Gg
KK
mm
uu
Rr
TT
7. Homozygous recessive
ee
Ff
HH
Oo
Uu
ww
8. Genotypes in which dominant gene must show
AA
Dd
EE
ff
Jj
RR
Ss
9. Genotypes in which recessive gene must show
aa
Gg
Ff
KK
rr
Oo
Tt
Part B: Punnett Squares
10. Examine the following Punnett squares and circle those that are correct.
D
d
D
D
A
a
A
a
d
Dd
dd
d
Dd
DD
A
AA
aa
a
Aa
aa
d
Dd
dd
d
Dd
Dd
a
Aa
Aa
a
Aa
aa
11. What do the letters on the outside of the Punnett square stand for?
Parent alleles
12. What do the letters on the inside of the Punnett square stand for?
Possible gerotypes
13. In corn plants, normal height, N, is dominant to short height, n. Complete these four Punnett squares
showing different crosses. Then, circle all of the homozygous dominant offspring. Put an X through all the
heterozygous offspring. Leave all the homozygous recessive offspring unshaded.
N
N
N.
n
N
n
n
Nn
N
Nn
n
N
NM
Nn
N
NNW
n
Nn
nr
n
NnNn
N
NMNH
n
NMN
n
Nnnn
