Rucete ✏ Biology In a Nutshell
1. What Is a Dihybrid Cross?
- A dihybrid cross examines the inheritance of two different traits simultaneously.
- Involves individuals that are heterozygous for both traits (e.g., YyRr).
2. Traits in Mendel’s Pea Plant Example
- Seed color:
- Y (yellow) = dominant
- y (green) = recessive
- Seed texture:
- R (round) = dominant
- r (wrinkled) = recessive
3. Parental (P) Generation
- YYRR (yellow round) × yyrr (green wrinkled)
- All F₁ offspring = YyRr (yellow round)
4. F₁ Generation Cross
- YyRr × YyRr
5. Possible Gametes
- Each YyRr parent can produce:
- YR, Yr, yR, yr
6. F₂ Generation Genotypes and Phenotypes
| Phenotype | Genotypes | Frequency |
|---|---|---|
| Yellow round | YYRR, YYRr, YyRR, YyRr | 9 |
| Green round | yyRR, yyRr | 3 |
| Yellow wrinkled | YYrr, Yyrr | 3 |
| Green wrinkled | yyrr | 1 |
- Phenotypic ratio: 9:3:3:1
In a nutshell
This classic Mendelian cross demonstrates the law of independent assortment:
Alleles of different genes assort independently during gamete formation.
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Biology in a nutshell