Dihybrid Crosses

Front

What is a dihybrid cross?

Back

A genetic cross that involves two traits, each represented by two alleles.

Front

What is the purpose of a Punnett square in a dihybrid cross?

Back

To predict the genotypes and phenotypes of offspring from two parents.

Front

How many boxes are needed in a Punnett square for a dihybrid cross?

Back

16 boxes are needed, representing all possible combinations of alleles.

Front

What does it mean for an organism to be heterozygous?

Back

It has two different alleles for a particular gene (e.g., Bb).

Front

What does it mean for an organism to be homozygous?

Back

It has two identical alleles for a particular gene (e.g., BB or bb).

Front

What is the phenotypic ratio of a typical dihybrid cross?

Back

The phenotypic ratio is typically 9:3:3:1.

Front

What are dominant alleles?

Back

Alleles that express their trait even when only one copy is present.

Front

What are recessive alleles?

Back

Alleles that express their trait only when two copies are present.

Front

In a dihybrid cross, what is the probability of obtaining a homozygous recessive offspring?

Back

1 out of 16, or 6.25%.

Front

What is the genotype of an offspring that is tall and white in a dihybrid cross?

Back

It can be either Ttww or TTww, depending on the dominant traits.