phenotypic and genotypic ratios are equal in

Options

A. incomplete dominance
B. Test cross
C. All monohybrid crosses
D. Both (1)&(2)

Answer

To solve the question regarding when phenotypic and genotypic ratios are equal, we can follow these steps:

### Step 1: Understand the Definitions
- **Phenotypic Ratio**: This is the ratio of different phenotypes (observable traits) in the offspring.
- **Genotypic Ratio**: This is the ratio of different genotypes (genetic makeup) in the offspring.

### Step 2: Identify the Context
- The question asks in which genetic scenario the phenotypic and genotypic ratios are equal. We need to consider different types of inheritance patterns.

### Step 3: Consider Incomplete Dominance
- In incomplete dominance, the heterozygous phenotype is distinct and intermediate between the two homozygous phenotypes. For example, if red (RR) and white (rr) flowers are crossed, the offspring (Rr) will be pink.
- The genotypic ratio for this cross (RR, Rr, rr) is 1:2:1, and the phenotypic ratio is also 1:2:1 (1 red: 2 pink: 1 white).

### Step 4: Analyze Other Options
- **Test Cross**: This involves crossing an individual with a dominant phenotype with a homozygous recessive individual. The phenotypic ratio will not equal the genotypic ratio because it depends on the unknown genotype of the dominant individual.
- **Monohybrid Crosses**: In typical monohybrid crosses (where one trait is considered), the phenotypic ratio is 3:1 while the genotypic ratio is 1:2:1.

### Step 5: Conclusion
- The only scenario where the phenotypic and genotypic ratios are equal is in **incomplete dominance**.

### Final Answer
The correct answer is **incomplete dominance**.

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