Biology 1B Section 11.2, Punnett Squares Heredity Biology 1B Section 11.2, Punnett Squares

Section 11.2 Objectives 4. Use punnett squares to predict the probability of genetic crosses   5. Discuss the design, results and conclusions of Mendel’s dihybrid cross experiment. 6. Explain the principle Independent Assortment

Punnett Squares A punnett square is a chart used to predict the probable results (offspring) from a genetic cross The punnett square is based on the principle of segregation Start with the parent genotypes Separate the alleles with equal probability

Completing a Punnett Square Let’s assume a cross between two heteozygous parents Bb x Bb Use the law of segregation to set up the punnett square One parent on top, the other on the side Separate the alleles with equal probability

Completing the Punnett Square Create allele pairs in the answer box by carrying parent alleles down and across The allele pairs will be the genotypes of the offspring

Completed Punnett Square From the cross Bb x Bb The genotypes of the offspring will be ¼ BB ½ Bb ¼ bb

Punnett Square Practice Complete Punnett Squares for the following crosses: BB x Bb Bb x bb bb x Bb bb x bb BB x bb