Question

which of the following statements correctly describes a dihybrid cross?
a dihybrid cross involves two parents.
a dihybrid cross produces two offspring.
a dihybrid cross involves organisms that are heterozygous for two characters.
a dihybrid cross results in a 3:1 phenotype ratio in the f2

Explanation:

A dihybrid cross is a cross between two individuals that are each heterozygous for two different genes (characters). For example, in pea plants, crossing \(YyRr\) (heterozygous for seed color \(Y/y\) and seed shape \(R/r\)) with another \(YyRr\) is a dihybrid cross.

• The first option “A dihybrid cross involves two parents” is too general. Many crosses involve two parents, not just dihybrid crosses.
• The second option “A dihybrid cross produces two offspring” is incorrect. A cross (whether dihybrid or not) can produce multiple offspring, and the number of offspring is not what defines a dihybrid cross.
• The fourth option “A dihybrid cross results in a \(3:1\) phenotype ratio in the \(F2\)” is wrong. A dihybrid cross (when following Mendelian genetics and independent assortment) results in a \(9:3:3:1\) phenotype ratio in the \(F2\) generation.

Answer:

A dihybrid cross involves organisms that are heterozygous for two characters.