Punnett SquaresPredicting offspring ratios from two parents' genes.9th GradeA Punnett square shows every possiblecombination of alleles from two parents,and how likely each is.MONOHYBRID CROSSAa × AaRATIO3 : 1Alleles are versions of a gene; you inherit one from each parent.Dominant alleles show even with one copy; recessive need two.Homozygous means two identical alleles; heterozygous means two different.Genotype is the alleles; phenotype is what you can see.Aa × Aa gives a 3 : 1 phenotype ratio and a 1 : 2 : 1 genotype ratio.LOOK FOR ITTwo heterozygous brown-eyed parents can have a blue-eyed child — a 1in 4 chance.A Punnett square gives probabilities, not guarantees. Four childrencan all be the same.Punnett Squareswww.littleactivity.com

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Science · 9th Grade

Punnett Squares

Predicting offspring ratios from two parents' genes.

How to use it

Write the parents' alleles on the outside first. The grid does the rest.

Free · print-ready PDF · US Letter and A4

Grade
9th Grade
Ages
14–15
Subject
Science
Pages
1

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