Which of the following best distinguishes a monohybrid cross from a dihybrid cross in classical genetics experiments?

• A. A monohybrid cross always produces four phenotypes, while a dihybrid cross produces only two.
• B. A monohybrid cross involves two different species, while a dihybrid cross involves only one species.
• C. A monohybrid cross examines the inheritance of a single gene, while a dihybrid cross examines two genes simultaneously.
• D. A monohybrid cross requires homozygous parents, while a dihybrid cross requires heterozygous parents.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the definition of a monohybrid cross. A monohybrid cross involves the study of inheritance of a single gene with two alleles, typically focusing on one trait.
2. Step 2: Understand the definition of a dihybrid cross. A dihybrid cross examines the inheritance of two different genes, each with two alleles, simultaneously, focusing on two traits.
3. Step 3: Compare the number of genes involved in each cross. A monohybrid cross involves one gene, while a dihybrid cross involves two genes.
4. Step 4: Recognize that the number of phenotypes produced depends on the number of genes and their alleles, not strictly on the type of cross. Therefore, the number of phenotypes is not a definitive way to distinguish between monohybrid and dihybrid crosses.
5. Step 5: Conclude that the best distinction is that a monohybrid cross examines one gene's inheritance, while a dihybrid cross examines two genes' inheritance simultaneously.