The fruit fly Drosophila melanogaster was found to be very suitable for experimental verification of chromosomal theory on inheritance by Morgan and his colleagues because

Options

A. (a) it reproduces parthenogenetically
B. (b) A single mating produces two young flies
C. (c) smaller female is easily recognizable from larger male
D. (d) It completes life cycle in about two weeks

Answer

**Step-by-Step Solution:**

1. **Introduction to Drosophila melanogaster**: Drosophila melanogaster, commonly known as the fruit fly, is a widely used model organism in genetic studies. Its characteristics make it suitable for experimental verification of genetic theories.

2. **Reproductive Method**: The fruit fly reproduces sexually, not parthenogenetically. This means that fertilization occurs between male and female gametes, leading to genetic variation in the offspring. Therefore, option A, which states that it reproduces parthenogenetically, is incorrect.

3. **Offspring Production**: A single mating of fruit flies does not produce just two young flies. In fact, a single mating can result in the production of approximately 100 to 200 offspring. This high reproductive rate makes them ideal for genetic studies. Thus, option B is also incorrect.

4. **Sexual Dimorphism**: In Drosophila, the female is larger than the male, which makes it easy to distinguish between the two sexes. However, the statement that the smaller female is easily recognizable from the larger male is incorrect. Therefore, option C is not valid.

5. **Life Cycle Duration**: One of the key reasons Drosophila melanogaster is favored for genetic research is that it completes its life cycle in about two weeks. This rapid life cycle allows researchers to observe multiple generations in a short period, facilitating genetic studies. Hence, option D is the correct statement.

6. **Conclusion**: Based on the analysis of the options, the correct reason why Drosophila melanogaster was suitable for experimental verification of the chromosomal theory of inheritance is that it completes its life cycle in about two weeks.

**Final Answer**: D. It completes its life cycle in about two weeks.

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