Reginald Punnett created the Punnett square, a diagram used to predict possible offspring genotypes and phenotypes from a genetic cross. A Punnett square works by writing the alleles of one parent across the top and the other parent down the side, then determining the genotypes and phenotypes of the offspring through combination. An example problem shows a black heterozygous female guinea pig mating with a white male, resulting in offspring with 25% BB, 50% Bb, and 25% bb genotypes, and 75% black and 25% white phenotypes.

1. Notes: Punnett squares (pg 8)

2. Notes: Punnett squares (pg 8)
• Punnett square = Diagram used to predict the
possible offspring of a cross

3. Notes: Punnett squares (pg 8)
• Punnett square = Diagram used to predict the
possible offspring of a cross
• Created by Reginald Punnett

4. Notes: Punnett squares (pg 8)
• Punnett square = Diagram used to predict the
possible offspring of a cross
• Created by Reginald Punnett
• The alleles of one parent are written across
the top of the square (one allele per box) and
those of the other parent are written on the
side

6. • Genotype frequency: 25% BB, 50% Bb, 25% bb

7. • Genotype frequency: 25% BB, 50% Bb, 25% bb
• Phenotype frequency: 75% Black, 25% White

8. Output (pg 9)
• Guinea pig diagram
• Tape as close to the top as you can

9. Example Problem (pg 8)
• In guinea pigs, black fur (B) is dominant to white
fur (b). A heterozygous black female mates with a
white male. What are the genotype and
phenotype ratios of the offspring?

10. Output (pg 9)
• Make up a problem that requires a Punnett
square to solve it. Write it on pg 9. Then trade
interactive notes with your neighbor and have
them try to solve it