A Punnett square to calculate genotype and phenotype ratios.

First the possible gametes of the two parents are aligned along two sides of a square.

Then the gametes are combined to show genotypes of potential zygotes in the cells of the square.

All the eggs of homozygous recessive (albino) mother have the recessive allele (m).
All the sperm of homozygous dominant (pigmented) father have the dominant allele (M).
All the offspring are heterozygous (Mm) in genotype, pigmented in phenotype.

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