How does a monohybrid cross Punnett square illustrate genotype and phenotype probabilities?

• A. It demonstrates the inheritance of a single trait with two alleles.
• B. It shows all offspring have the same genotype as the parents.
• C. It shows offspring genotypes in a 1:2:1 ratio and corresponding phenotype ratios based on dominance.
• D. It cannot predict any phenotype outcomes.

Answer: (C)

A monohybrid cross Punnett square shows how two alleles for a single trait segregate and combine to form offspring, revealing both genotype and phenotype probabilities. When you cross two heterozygotes for a trait with two alleles, listing the possible gametes from each parent (A and a) and pairing them in a Punnett square gives four possible offspring genotypes: AA, Aa, Aa, aa. That results in a genotypic ratio of 1:2:1. How those genotypes appear as traits depends on dominance: if the dominant allele masks the recessive, both AA and Aa express the dominant phenotype, while aa expresses the recessive phenotype. So you get a phenotypic pattern that reflects the dominance relationship—typically a 3:1 dominant-to-recessive ratio in the classic complete dominance case. The Punnett square thus visualizes the chances of each genotype and, through dominance, the corresponding phenotype probabilities. If dominance isn’t complete, the phenotype ratios would shift accordingly, but the genotype 1:2:1 pattern still underlies the prediction.