Worked Example Let students accomplish Activity 4.3: Patterns of Inheritance Assign groups to present their work in class and check students' answers. 4.Seed Color and Seed Shape in Pea Plants In pea plants, seed color and seed shape are controlled by two separate genes. Seed color is determined by the Y gene, where Y represents the dominant allele for yellow seeds, and y represents the recessive allele for green seeds, Seed shape is controlled by the S gene, where S represents the dominant allele for smooth seeds, and s represents the recessive allele for wrinkled seeds Parent 1 is homozygous dominant for seed color (YY) and heterozygous for seed shape (Ss), producing yellow smooth seeds. Parent 2 is heterozygous for seed color (Yy) and homozygous recessive for seed shape (ss), yielding green wrinkled
Answer (1)
We will solve this using a Punnett square approach for two traits: Color (Yy) and Shape (Ss).Step 1: Determine gametesParent 1 (YY Ss):Gametes = YS, Ys (since YY always gives Y, and S can be S or s)Parent 2 (Yy ss):Gametes = Ys, ys (since s is always s, and Y or y for color)Step 2: Cross the gametes YS (P1) Ys (P1)Ys (P2) YY Ss (yellow, smooth) YY ss (yellow, wrinkled)ys (P2) Yy Ss (yellow, smooth) Yy ss (yellow, wrinkled)Step 3: Phenotype ratio of offspringAll offspring have Y, so all will have yellow seeds (dominant trait shows).For shapeSs = smoothss = wrinkledResults2 out of 4 = yellow, smooth (YY Ss or Yy Ss)2 out of 4 = yellow, wrinkled (YY ss or Yy ss)Final Phenotype Ratio50% yellow, smooth50% yellow, wrinkledSummaryThe offspring will all have yellow seeds, but half will be smooth, and half will be wrinkled.
