• Morgon carried out several dihybrid crosses in Drosophila to study genes that were sex-linked.
• For example, Morgon crossed between9 yellow-bodied, white-eyed females to brown-bodied; red-eyed males and intercrossed their F1 progeny.
• He observed that the two genes did not segregate independently of each other and also observed that the F2 ratio deviated very significantly from the 9:3:3:1 ratio.
• Morgan’s findings different from Mendel’s because of thephenomena of linkage and recombination.
• On the same chromosomes, some genes are tightly linked showed very less recombination where as others were loosely linked showed higher recombination.
• For example, he found that the genes showed only 1.3 per cent recombination but white and yellow were tightly connected and whereas white and miniature wing showed 37.2 per cent recombination.
Figure. Linkage: results of two dihybrid crosses conducted by Morgan.
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