Question

A test cross is performed between:

• A. Heterozygote (F$_1$) $\times$ Recessive
• B. Two homozygotes
• C. Dominant $\times$ Dominant
• D. Recessive $\times$ Recessive

Hint:

Test cross = Unknown dominant × Homozygous recessive

Answer 1

The Correct Option is A

Concept:
A test cross is used to determine the genotype of an individual showing dominant phenotype by crossing it with a homozygous recessive individual.

Step 1: Purpose of Test Cross

• To identify unknown genotype
• Particularly useful for dominant traits

Step 2: Genetic Principle

• If individual is homozygous dominant → all offspring dominant
• If heterozygous → offspring show 1:1 ratio

Step 3: Required Cross

• Unknown dominant phenotype (usually F$_1$ heterozygote)
• Crossed with homozygous recessive

Step 4: Evaluating Options

• Two homozygotes → not test cross
• Dominant × Dominant → cannot reveal genotype
• Recessive × Recessive → no variation Final Conclusion: \[ \boxed{\text{Heterozygote} \times \text{Recessive}} \]