Punnett Squares Practice

Punnett Squares Practice

Read each question carefully and fill in the Punnett squares and answers as directed. Remember to use uppercase letters for dominant alleles and lowercase letters for recessive alleles.

Punnett squares are diagrams used to predict the probability of an offspring inheriting certain traits from its parents. They help us understand how alleles (different forms of a gene) combine during reproduction.

1. A Punnett square is a tool used to predict the   of an offspring inheriting certain traits.

2. Different forms of a gene are called  .

3. A   allele is represented by an uppercase letter.

4. A   allele is represented by a lowercase letter.

In pea plants, tall (T) is dominant over short (t). A homozygous tall pea plant (TT) is crossed with a homozygous short pea plant (tt).

1. Fill in the Punnett Square below for this cross.

2. What percentage of the offspring will be tall?

3. What percentage of the offspring will be short?

1. If a heterozygous tall pea plant (Tt) is crossed with another heterozygous tall pea plant (Tt), what is the expected genotypic ratio of the offspring?

2. What is the phenotypic ratio for the cross described in question 1?

In a certain breed of dog, black fur (B) is dominant over brown fur (b). A breeder crosses a heterozygous black dog (Bb) with a brown dog (bb).

1. Draw and fill in a Punnett Square for this cross in the space below.

2. What is the probability of having offspring with black fur?

3. What is the probability of having offspring with brown fur?