Q1. [1] deep exam-ready
Two pea plants, one with genotype TTWW (tall, violet flowers) and another with ttww (short, white flowers) are crossed. The F1 progeny are all tall with violet flowers. When F1 plants are self-pollinated, which new phenotypic combinations are expected in F2 that were NOT present in either parent?
- A Tall with violet flowers and short with white flowers only
- B Tall with white flowers and short with violet flowers
- C Only short plants with white flowers
- D No new combinations; only parental types reappear
Generated by claude-sonnet-4-6 · 2026-06-26 01:02 · grounding rag
Model Answer
Answer: B — Tall with white flowers and short with violet flowers
In F2, independent assortment produces new combinations (TtWw × TtWw) not seen in either parent (TTWW or ttww).
Explanation
- Parents are TTWW (tall, violet) and ttww (short, white); F1 is TtWw.
- F1 self-pollination gives 9:3:3:1 ratio — the 3:1 minority classes (tall+white and short+violet) are new recombinant phenotypes.
- The textbook explicitly states: "there would also be some F2 progeny that showed new combinations" when two traits are independently inherited — directly supporting option B.
- Options A and D describe only parental types; C describes only one parental type. Only B correctly identifies both new recombinant combinations.