Punnett Squares

Front

What is a Punnett Square?

Back

A Punnett Square is a diagram used to predict the genetic makeup of offspring from a cross between two parents.

Front

What does a dominant allele mean?

Back

A dominant allele is an allele that expresses its trait even when only one copy is present in the genotype.

Front

What does a recessive allele mean?

Back

A recessive allele is an allele that only expresses its trait when two copies are present in the genotype.

Front

In a Punnett Square, what does each box represent?

Back

Each box represents a possible genotype of the offspring and the probability of that genotype occurring.

Front

What is the genotype for brown eyes if brown is dominant over blue?

Back

The genotype for brown eyes can be either homozygous dominant (BB) or heterozygous (Bb).

Front

If a parent has a genotype Bb and the other has bb, what is the probability of having a child with blue eyes?

Back

The probability is 50%.

Front

What is the phenotype of a homozygous recessive genotype?

Back

The phenotype of a homozygous recessive genotype is the trait that is expressed by the recessive allele.

Front

What is the difference between homozygous and heterozygous genotypes?

Back

Homozygous genotypes have two identical alleles (e.g., TT or tt), while heterozygous genotypes have two different alleles (e.g., Tt).

Front

If tall (T) is dominant over short (t), what is the phenotype of TT?

Back

The phenotype of TT is tall.

Front

What is the expected genotype ratio from a cross between Tt and Tt?

Back

The expected genotype ratio is 1 TT : 2 Tt : 1 tt.