Punnett square worksheet
Complete the following problems. List the parent genotypes, draw and fill in a Punnett square, and then list the offspring genotypes
and phenotypes.
1.
A homozygous dominant brown mouse is crossed with a homozygous tan mouse (tan is the recessive color).
2.
A heterozygous white (brown fur is recessive) rabbit is crossed with a homozygous brown rabbit.
3.
Two homozygous red flowers (white flowers are recessive) are crossed.
4.
A heterozygous tall plant is crossed with a homozygous tall plant (short is the recessive size).
5.
A heterozygous blue flower is crossed with a homozygous black flower.
Congratulations! You have done very well in learning the monohybrid Punnett squares.
Now it is time to move on to something a little more challenging.
Steps to Solving Dihybrid Punnett Squares
1) Determine the parent gene types. 2) Determine the possible gene pairs donated by each parent. 3) Fill
in the Punnett square. 4) Determine the possible offspring phenotypes.
Example:
A tall green pea plant that is homozygous dominant for both traits is crossed with a short yellow
pea plant that is homozygous recessive for both traits. Show the test cross.
1) Parent gene types
Parent 1 = (T T G G)
Parent 2 = (t t g g)
2) Possible gene pairs donated by each parent
Parent 1: TG, TG, TG, TG
Parent 2: tg, tg, tg, tg
3) Fill in the Punnett Square
tg
tg
tg
tg
TG
TG
TG
TG
TtGg
TtGg
TtGg
TtGg
TtGg
TtGg
TtGg
TtGg
TtGg
TtGg
TtGg
TtGg
TtGg
TtGg
TtGg
TtGg
Determine offspring phenotypes
Tall/Green 16 : Tall/Yellow 0 : Short/Green 0 : Short/Yellow 0
Now try this problem at your desk
1.) A long neck yellow giraffe (T t Y y), mates with a short neck orange giraffe (t t y y).
___________ X ___________
Phenotype Ratio:
Long/Yellow____ : Long Orange ____ : Short/Yellow ____ : Short/Orange____