In 1910, a geneticist named Thomas Morgan conducted experiments with fruit flies. When mutant fruit flies with white eyes were crossed with normal fruit flies with red eyes, the offspring had either red or white eyes. The flies with white eyes were almost always male. Eye color in these fruit flies is an example of which type of trait?

Thomas Hunt Morgan is known for his chromosomal theory of inheritance in which he showed that traits are controlled by the factors called genes arranged in the linear fashion on chromosomes.

He proposed the theory after he performed the experiments on Drosophila when he studied the pattern of inheritance of color of the eye.

He crossed the normal red-eyed females with white-eyed males and found that in F₁ generation all the red-eyed offsprings are produced. When he crossed the F₁ generation he found that during F₂ generation red-eyed females and white-eyed males were produced.

He suggested that the color of the eye is related to the sex of the Drosophila and concluded that the color of the eye is a sex-linked trait.

Thus, a sex-linked trait is the correct answer.