Based on Mendel's experiment show the cross between round, yellow seeds of pea plant (RRYY) with wrinkled and green seeds of pea plant (rryy) upto F2 generation. Write the number of seeds/plants with following genetic (Genotype) makeup in F2 generation :
(i) RRYY
(ii) rryy
Generated by claude-sonnet-4-6 · 2026-06-15 06:51 · grounding rag
Model Answer
Cross: RRYY × rryy
F₁ Generation:
All F₁ plants are RrYy (round, yellow) — dominant traits appear.
F₂ Generation (F₁ × F₁: RrYy × RrYy):
| | RY | Ry | rY | ry |
|---|---|---|---|---|
| RY | RRYY | RRYy | RrYY | RrYy |
| Ry | RRYy | RRyy | RrYy | Rryy |
| rY | RrYY | RrYy | rrYY | rrYy |
| ry | RrYy | Rryy | rrYy | rryy |
F₂ phenotypic ratio = 9 : 3 : 3 : 1 (out of 16 combinations)
(i) RRYY — 1 plant out of 16
(ii) rryy — 1 plant out of 16
Source: Chapter 8 – Heredity, Section 8.2.3 (Figure 8.5)
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Explanation
- The question asks for a dihybrid cross up to F₂; draw the Punnett square clearly.
- Note: The textbook (Fig. 8.5) shows RRyy × rrYY, but the question uses RRYY × rryy. The F₁ is still RrYy and the F₂ Punnett square is identical.
- Both RRYY and rryy appear once each in the 4×4 Punnett square (1/16 each). Examiners award marks for the correct Punnett square AND the specific counts.
- Always state F₁ genotype before drawing F₂.