Punnett Squares

Front

What is a Punnett Square?

Back

A Punnett Square is a diagram used to predict the outcome of a genetic cross by showing the possible combinations of alleles from the parents.

Front

What does homozygous mean?

Back

Homozygous means that the two alleles for a trait are the same (e.g., TT or tt).

Front

What does heterozygous mean?

Back

Heterozygous means that the two alleles for a trait are different (e.g., Tt).

Front

What is a dominant allele?

Back

A dominant allele is one that expresses its trait even when only one copy is present (e.g., T in Tt).

Front

What is a recessive allele?

Back

A recessive allele is one that only expresses its trait when two copies are present (e.g., tt).

Front

In a Punnett Square, what does each box represent?

Back

Each box in a Punnett Square represents a possible genotype of the offspring from the genetic cross.

Front

What is the probability of getting a dominant trait from a heterozygous parent (Tt) and a homozygous recessive parent (tt)?

Back

The probability is 50% for the dominant trait.

Front

If T = tall and t = short, what are the possible genotypes from a cross of TT and tt?

Back

The possible genotype is all Tt (tall).

Front

What is the phenotypic ratio of a monohybrid cross between two heterozygous parents (Tt x Tt)?

Back

The phenotypic ratio is 3 tall: 1 short.

Front

What does it mean if a trait is expressed in 75% of the offspring?

Back

It means that the trait is dominant and likely comes from at least one dominant allele in the parents.