Genotype and Phenotype Probabilities

Patterns of genetic inheritance obey the laws of probability. In a monohybrid cross, where the allele^*s present in both parents are known, each genotype^* shown in a Punnett Square^* is equally likely to occur. Since there are four boxes in the square, every offspring produced has a one in four, or 25%, chance of having one of the genotypes shown.

Like flipping a coin, previous matings do not influence the results of subsequent matings. Because of random variation, the actual number of each genotype produced over a series of matings (or crosses) between two individuals will differ slightly from the expected 25% per box.

The illustration above explores how the probabilities predicted by a monohybrid Punnett Square relate to the actual pattern of genotypes and phenotype^*s produced from repeatedly crossing two individuals.

Test your understanding of genotype and phenotype probabilities

Video Overview

Related Content

• Illustrations
  • Alleles, genotype and phenotype
  • Punnett Square
• Problem Sets
  • Allele, genotype and Phenotype questions
  • Punnett Square Practice Problems
  • Monohybrid genotype and phenotype probability questions