Q.Who had proposed the chromosomal theory of the inheritance?

Morgan's Fruit Fly Experiments: A First Look

Imagine you're trying to understand how traits pass from parents to children. You could study humans, but that takes decades — one generation every 25 years. What if you could watch a hundred generations in a single year? That's exactly what Thomas Hunt Morgan realised when he picked the fruit fly, Drosophila melanogaster, for his experiments around 1910.

Why Fruit Flies?

Morgan needed an organism that was cheap, fast-breeding, and easy to handle. Fruit flies fit perfectly. They breed every 10–14 days, produce hundreds of offspring, and have just four pairs of chromosomes — simple enough to track. More importantly, they show clear, visible traits: eye colour (red or white), wing shape (normal or vestigial), body colour (grey or black). These traits became Morgan's window into how genes work.

The Breakthrough: The White-Eyed Male

Morgan started by breeding normal red-eyed flies. Then, by chance, he found a single male with white eyes — a mutant. He crossed this white-eyed male with a red-eyed female. All the offspring (the F1 generation) had red eyes. That told him red eye colour was dominant over white.

Then came the crucial step. He bred those F1 red-eyed flies with each other. In the F2 generation, he got a surprise: all the females had red eyes, but half the males had white eyes. The white-eye trait appeared only in males.

What Morgan Proved

Before Morgan, scientists knew chromosomes existed, but no one had proven that a particular gene lived on a particular chromosome. Morgan's fruit fly experiments did exactly that. He showed that:

• Genes are physical units located on chromosomes
• The inheritance of a trait (white eyes) follows the inheritance pattern of a specific chromosome (the X)
• Sex-linked traits — those carried on the X chromosome — behave differently in males and females

This was the birth of the chromosomal theory of inheritance. It connected Mendel's abstract "factors" (genes) to real, visible structures inside cells.

Why It Matters for a Commerce/Humanities Student

You might think this is pure biology, but the principle here is about evidence linking a cause to an effect. Morgan didn't just guess that genes were on chromosomes — he designed an experiment where the pattern of inheritance forced that conclusion. This is the same logic used in economics (linking policy changes to market outcomes) or law (linking evidence to a verdict). The method matters as much as the result. …