Morgan carried out several dihybrid crosses in Drosophila and found F₂-ratios deviated very significantly from the expected Mendelian ratio. Explain his findings with the help of an example.

Question

Morgan carried out several dihybrid crosses in Drosophila and found F 2 -ratios deviated very significantly from the expected Mendelian ratio. Explain his findings with the help of an example.

Philoid · Accepted Answer

• 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.

Note:

Figure. Linkage: results of two dihybrid crosses conducted by Morgan.

Morgan carried out several dihybrid crosses in Drosophila and found F2-ratios deviated very significantly from the expected Mendelian ratio. Explain his findings with the help of an example.

Morgan carried out several dihybrid crosses in Drosophila and found F₂-ratios deviated very significantly from the expected Mendelian ratio. Explain his findings with the help of an example.