Morgan carried out several cross in Drosophila to study genes that were

Options

A. sex-linked
B. autosomal
C. involved in sex determination
D. segregated independently

Answer

### Step-by-Step Text Solution

1. **Understanding Drosophila as a Model Organism**:
- Drosophila melanogaster, commonly known as the fruit fly, is a widely used model organism in genetics due to its simple genetic structure, short life cycle, and ease of breeding.

2. **Identifying Chromosomal Structure**:
- In Drosophila, females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). This chromosomal difference is crucial for understanding inheritance patterns.

3. **Sex-Linked Traits**:
- Morgan studied traits that are linked to the sex chromosomes, particularly those that are located on the X chromosome. An example is the eye color trait, where the gene responsible for eye color is found on the X chromosome.

4. **Expression of Sex-Linked Traits**:
- Males express all traits linked to their single X chromosome because they do not have a second X chromosome to mask the trait. In contrast, females require the trait to be present on both X chromosomes to express it.

5. **Morgan's Observations**:
- In his experiments, Morgan observed that in the first generation of flies, all males exhibited white eyes, while females did not show this trait. This was due to the fact that the gene for white eyes was present on the X chromosome, and since males have only one X chromosome, they displayed the trait.

6. **Conclusion on Morgan's Research**:
- Morgan's work demonstrated the concept of sex-linked inheritance, particularly how certain traits are expressed differently in males and females due to their chromosomal differences. He carried out several crosses to study these sex-linked traits, as well as traits that were autosomal and those that segregated independently.