A Punnett square is a combinatorial grid that enumerates every equally likely pairing of parental gametes, converting the genotypes of two parents into the complete distribution of offspring genotypes and, through the applicable dominance rule, into the distribution of phenotypes. Its generality does not depend on simple dominance: the same enumeration applies under incomplete dominance (the heterozygote expresses an intermediate blended phenotype), under codominance (both alleles are fully expressed simultaneously), and to multiple-allele systems where dominance relationships differ between allele pairs; extended to two loci that assort independently, it becomes the dihybrid cross, whose 16 cells yield the classic 9:3:3:1 phenotypic ratio. This material belongs to Mendelian genetics and connects the chromosomal theory of inheritance — independent assortment for loci on different chromosomes, linkage for loci on the same chromosome — to probabilistic prediction of inheritance patterns.
A Punnett square is a combinatorial grid that enumerates every equally likely pairing of parental gametes, converting the genotypes of two parents into the complete distribution of offspring genotype…