Punnett Squares

Sample Problem In peas, yellow is dominant to green. A homozygous green pea plant is crossed with a heterozygous yellow pea plant. What is the phenotype ratio of the next generation?

Punnett Square Use 1. Write a let statement! Let capital letter = dominant trait Lowercase letter = recessive 2. Determine the parent’s genotypes (letters). 3. Draw Punnett Square. 4. Fill in Punnett Square. 5. Answer question.

Sample Problem In peas, yellow is dominant to green. A homozygous green pea plant is crossed with a heterozygous yellow pea plant. What is the phenotype ratio of the offspring? Solution: Let Y = yellow, y = green Homozygous green: yy Heterozygous yellow: Yy

yy x Yy y y Y Y Y y y y y y y y Solution: Phenotype ratio: 2 yellow : 2 green y y Y Y Y y y y y y y y