Genetics Punnett Squares

Genetics- Punnett Squares

A Punnett square is a diagram used in genetics to predict the possible genotypes (genetic makeups) of offspring from two parents. It is named after Reginald C. Punnett, who devised the approach in 1905.
It works by placing one parent's alleles (gene variants) along the top row and the other parent's alleles along the side column.
Each box within the square shows a combination of one allele from each parent, representing a potential genotype for their offspring.

Vocabulary REMINDER

Heredity: refers to the passing of traits or characteristics from
parents to their offspring through the transmission of genetic
information
Genes: a segment of DNA that encodes a specific trait or
characteristic
Allele: a variant of a gene that occupies a specific location on a
chromosome An individual inherits two alleles, one from each
parent, for any given genomic location where such variation
exists

​Homozygous Dominant and Homozygous Recessive are considered PUREBRED because both alleles are the same

Multiple Choice

Which of the following alleles is purebred recessive?

• Tt

• tt

• TT

Match

Match the following

• BB

• Bb

• bb

Homozygous Dominant

Heterozygous

Homozygous Recessive

• Homozygous Dominant

• Heterozygous

• Homozygous Recessive

​PHENOTYPE
is the physical
expression of the genotype - like brown eyes

Multiple Choice

Aa, DD, Ba, and yy are all examples of ---

• genotypes

• phenotypes

Step By Step Punnett Square

1. Determine the genotypes of the parents.

2. Write down the possible allele for each parent.

3. Arrange the parents' alleles around the edges of a Punnett square.

4. Fill out the offspring squares.

5. Interpret the results (probability of phenotypes)

​each square is a 25% probability, so for the above square is 50% yellow 50% green

• we will focus on 1 trait at a time with 2 alleles per trait for this section!

Multiple Choice

Each one of the boxes on the Punnett square represents what probability of an offspring's genotype?

• 25%

• 1%

• 10%

• 0%

Multiple Choice

B = brown fur b = white fur

In the punnett square, what is the probability for white fur?

• 0%

• 25%

• 50%

• 75%

Multiple Choice

T - tall and t = short

In the Punnett square, what belongs in the missing square?

• tt

• Tt

• TT

Multiple Choice

G = green, g = yellow

The genotype for a yellow plant is...

• GG

• Gg

• gg

• all of the choices result in yellow