Thomas hunt Morgan experiment

• Thomas Hunt Morgan was awarded the Nobel Prize in Physiology or Medicine in 1933.
• The work for which the prize was awarded was completed over a 17-year period at Columbia University, commencing in 1910 with his discovery of the white-eyed mutation in the fruit fly, Drosophila.
• Morgan carried out several dihybrid crosses as carried out by mendel in peas.
• He carried out several crosses in Drosophila to study the genes that are Sex-linked.
• He observed that when the two genes in a dihybrid cross are located on the same chromosomes, the proportion of parental genes combination in the progeny was higher than the non- parental or recombination of genes.
• when the genes are loosely linked they show higher percenteage of recombination.

Why Morgan used only drosophila Melanogaster for his Experiment?

• It could be grown on simple synthetic medium in laboratory.
• The fly has a short life cycle of about two weeks.
• A single mating produces hundreds of offspring.
• Females are easily distinguishable from the males by the laner bon Wave larger body size and presence of ovipositor(egg laying structure)
• It has many types of heredity variation that can be seen with low power microscopes.

Result

• In both crosses he found that the ratio obtained is not similar to the Mendel’s ratio of dihybrid cross i.e. 9:3:3:1 in F2
  generation.
• Mendel’s law of independent assortment was not taking place in this case. From this Morgan got the idea of linkage.

Reason

• He worked on the behaviour of the chromosomes to know the reason behind recombination. He said that these genes were located on X-chromosomes. They were present on same chromosomes so linkage concept was wined by Morgan.
• Linkage genes are those genes which are present on same chromosomes. They do not show independent assortment.
• According to him there is a physical Association between the genes of same chromosomes and Morgan coined this linkage. Due to linkage parental type appears in offspring in majority. Because parental gene combination was very much higher than the non- parental gene combination and those who are non-parental are called recombinant type.