CBSE 2026 · Region 3 · Set 1 · Q28 · 3 marks
(a)Describe the experiment conducted by T.H. Morgan on Drosophila melanogaster involving eye colour and body colour.(b)How did the results deviate from Mendelian inheritance pattern ?(c)Explain the two genetic terms used by Morgan for his observations.
(a)
Describe the experiment conducted by T.H. Morgan on Drosophila melanogaster involving eye colour and body colour.
(b)
How did the results deviate from Mendelian inheritance pattern ?
(c)
Explain the two genetic terms used by Morgan for his observations.
Marking-scheme solution
(a)
Morgan hybridised yellow bodied white eyed females with brown bodied red eyed males and inter-crossed their progeny.
(b)
He observed that the two genes did not segregate independently of each other as in Mendelian inheritance pattern
The ratio deviated from $\displaystyle 9$:$\displaystyle 3$:$\displaystyle 3$:$\displaystyle 1$ ratio (expected when genes segregate independently)
(c)
• Linkage - He gave this term to describe the physical association of the
two genes present on the same chromosome.
• Recombination - Generations of nonparental gene combinations.
Principles of Inheritance and VariationInheritance of Two GenesUnderstandshort_answermedium
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CBSE Class 12 Biology past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.