Advanced Placement (AP) Biology Practice Exam

What type of traits are studied in a monohybrid cross?

1. Only dominant traits

2. Only recessive traits

3. One pair of contrasting traits

4. Multiple pairs of traits

The correct answer is: One pair of contrasting traits

In a monohybrid cross, the primary focus is on the inheritance patterns of a single pair of contrasting traits for a particular characteristic. This involves studying how these two traits—one dominant and one recessive—are passed from parents to offspring. The classic example often used in genetics is Mendel's pea plant experiments, where he examined traits such as plant height (tall vs. short) or seed color (yellow vs. green). By analyzing just one pair of traits, researchers are able to understand the basic principles of inheritance, including concepts such as dominant and recessive alleles, genotype and phenotype ratios, and the predictability of traits in offspring based on the parental genotype. This simplified approach allows for clearer insights into the mechanics of inheritance without the complexities introduced by examining multiple traits simultaneously, which would occur in a dihybrid or more complex cross.