Biology 30 Genetics Practice Test 2026 - Free Genetics Practice Questions and Study Guide

Probability is about how likely different outcomes are. In genetics, it tells us the chance that a cross will produce certain genotypes or phenotypes, based on the alleles the parents carry. For example, when two heterozygotes are crossed, the Punnett square shows the possible allele combinations and their probabilities (like 1/4 for a particular genotype, 1/2 for another), letting us predict what fraction of offspring we expect to see. The other terms describe what we observe or inherit: a ratio expresses the relative frequencies after many offspring, a phenotype is the visible trait, and a genotype is the actual genetic makeup. So the term that describes the possibility or likelihood of outcomes is probability.