Chromosomal Inheritance in Fruit Flies

Chromosomal Inheritance and Thomas Morgan's Discoveries

• Thomas Morgan was the first to associate a specific gene with its corresponding chromosome.
• Utilized the fruit fly, Drosophila melanogaster, for genetic studies due to its rapid breeding cycle and manageable number of chromosomes.

Reasons for Using Fruit Flies

• Fruit flies breed quickly and produce a large quantity of offspring that can reproduce in approximately two weeks.
• They possess only four pairs of chromosomes, including three pairs of autosomes and one pair of sex chromosomes.

Initial Findings

• Wild-type fruit flies typically exhibit red eyes.
• After a year of breeding, Morgan identified a white-eyed male fruit fly, representing a mutant phenotype.
• Crossed a white-eyed male (mutant) with a red-eyed female (wild type).

Genetic Crosses

• Initial cross between white-eyed male (rr) and red-eyed female (RR) produced F1 generation, all of which had red eyes (Rr genotype).
• In a subsequent cross of the F1 generation (Rr x Rr), the offspring showed a Mendelian ratio:
  • 3:1 ratio of red-eyed to white-eyed flies.
  • All females were red-eyed, with males showing 50% red-eyed and 50% white-eyed.

Sex-Linked Genes

• Genes located on sex chromosomes (X or Y) known as sex-linked genes.
• This concept applies to various organisms, including humans, plants, and insects.

Linked Genes

• Each chromosome contains hundreds to thousands of genes.
• Genes that are located on the same chromosome are frequently inherited together, as they function as a single unit during genetic crosses.

Explore the process of chromosomal inheritance in fruit flies, as pioneered by Thomas Morgan. Learn about the characteristics of fruit flies and why they were chosen for genetic studies, and delve into the fascinating world of gene association with specific chromosomes.