Introduction to Punnett Squares

Intro to Punnett Square

Multiple Choice

What is an example of a phenotype?

• FF

• freckles

• ff

• Someone who can jump high

Punnett Square

Used to determine the PROBABILITY or
likelihood that certain genotypes and
phenotypes will occur.

Multiple Choice

What is the purpose of a Punnett Square?

• To determine why someone is interested in a sport

• determine the PROBABILITY or likelihood that certain genotypes and phenotypes will occur

• To determine the probability what career someone will choose in life

Punnett Square Video Explanation

Multiple Choice

Which is an example of homozygous dominant?

• TT

• Tt

• tt

Multiple Choice

Which is an example of heterozygous?

• BB

• Bb

• bb

Multiple Choice

What is an example of homozygous recessive?

• Pp

• PP

• pp

Punnett Square

Parent 1-

Parent 2 –

F1 Generation

T

t

t

t

Genotype:

Heterozygous
Homozygous Recessive

Phenotype:

Tall
Short

Punnett Square

Parent 1-

Parent 2 –

T

t

T

t

Genotype:

Homozygous Dominant __: 4
Heterozygous __:4
Homozygous Recessive __:4

Phenotype:

Tall __:4
Short __:4

Punnett Square

Parent 1-

Parent 2 –

T

T

t

t

Genotype:

Phenotype:

Let’s Practice

Everyone in Squidward’s family has light blue skin, which is the dominant trait for body color in his
hometown of Squid Valley. His family brags that they are a “purebred” line. He recently married a
nice girl who has light green skin, which is a recessive trait. Create a Punnett square to show the
possibilities that would result if Squidward and his new bride had children. Use B to represent the
dominant gene and b to represent the recessive gene.

B. What are the chances of a child
with light blue skin? ____%

C. What are the chances of a child
with light green skin? ____%

D. Would Squidward’s children
still be considered purebreds?
Explain!