Class 12 · Principles of Inheritance and Variation

Morgan's Fruit Flies and Chromosomal Theory — NEET Biology

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Following this synthesis of ideas, experimental verification of the chromosomal theory of inheritance by Thomas Hunt Morgan and his colleagues, led to discovering the basis for the variation that sexual reproduction produced. Morgan worked with the tiny fruit flies, Drosophila melanogaster, which were found very suitable for such studies. They could be grown on simple synthetic medium in the laboratory. They complete their life cycle in about two weeks, and a single mating could produce a large number of progeny flies. Also, there was a clear differentiation of the sexes – the male and female flies are easily distinguishable. Also, it has many types of hereditary variations that can be seen with low power microscopes.

🖼️Related NCERT figure: Two illustrations of Drosophila melanogaster fruit flies showing sexual dimorphism - (a) shows the male and (b) shows the female (Figure 4.10 Drosophila melanogaster (a) Male (b) Female)
NCERT Biology · Class 12 · Chapter 4 · Paragraph 59
How NTA Uses This Concept

NTA tests whether students understand why Drosophila melanogaster was chosen for genetic studies—not just what Morgan discovered, but WHY these flies were ideal. The core concept is that Morgan used fruit flies to experimentally verify that genes are located on chromosomes. Students often mistake this by confusing correlation with causation, or forgetting the practical advantages (short life cycle, large progeny, visible variations, distinct sexes). To get it right: remember the 'why' behind Drosophila selection. NEET frequently asks which organism was used and what advantages it offered—know that two-week life cycles and hundreds of offspring per mating made it perfect for tracking inheritance patterns across generations.

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Experimental verification of the chromosomal theory of inheritance was done by: (NEET 2020)

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