Section 3: Genetics, Cellular and Molecular Biology
Classical Genetics and Epistasis
Subtopic: Mendelian Genetics & Gene Interactions
Question Statement:
In a Mendel's dihybrid experiment
low seeds crossed with honor mom med n
seeds.
F, intercross produced 560 F, progeny. The number of F, progeny having
both dominant traits (round and yellow) is _
Official Answer Key:
315
Step-by-Step Solution & Explanation
### **Step-by-Step Solution & Mathematical Derivation (GATE BT 2021 Q.49)**
**1. Governing Concept & Definition**:
- **Topic**: Classical Mendelian Genetics & Dihybrid Cross
- In a classic Mendelian dihybrid cross involving two independently assorting traits (Round/wrinkled and Yellow/green), the phenotypic ratio among $F_2$ progeny is:
$9 : 3 : 3 : 1$
- The expected fraction exhibiting both dominant traits (Round and Yellow) is $\frac{9}{16}$.
**2. Detailed Step-by-Step Calculation**:
- **Given**:
- Total $F_2$ progeny $= 560$
- **Expected Number of Double Dominant Phenotypes**:
$N = 560 \times \frac{9}{16} = 35 \times 9 = 315$
**3. Final Answer**:
- **Calculated Value**: **315**
- **Official GATE Accepted Range**: **315 to 315**
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