In a pea plant cross, a plant heterozygous for seed colour (Rr) is crossed with a homozygous recessive plant (rr). What proportion of the offspring will have purple seeds?
Answer
50%
The correct answer is 50% — Express the proportion as a fraction and then as a percentage: (2/4)×100 = 50%.
Step-by-step solution
- Identify the genotypes of the parents: one parent is Rr and the other is rr.
- Draw a Punnett square with R and r from the first parent and r and r from the second parent.
- Determine the genotypes of the four possible offspring: Rr, Rr, rr, rr.
- Count the number of purple (dominant) phenotypes: two out of four.
- Express the proportion as a fraction and then as a percentage: (2/4)×100 = 50%.
Common mistake: Treating the heterozygous parent as if it were recessive
Concept tested: Mendelian dominant/recessive inheritance
Published · How this solution was prepared and checked
← All Principles of Inheritance and Variation questions