Question

In Morgan's initial cross, red-eyed females (XR XR) were crossed with white-eyed males (Xr Y). What observation did Morgan make in the F₂ generation?

Options

• A 1:1:1:1 ratio was observed as expected

• White eyes appeared only in males in an unequal ratio

• White eyes appeared equally in males and females

• All offspring had white eyes

Answer 1

Morgan observed that the F₂ generation showed an unequal ratio with white eyes appearing only in males, rather than the expected 1:1:1:1 ratio. This deviation from Mendelian expectations led to the discovery that the white-eye gene is located on the X chromosome, demonstrating sex-linked inheritance.