What is the role of Linked Traits in genetics?

In his study of inheritance in the fruit fly, Morgan observed that certain genes are distributed together, or linked, rather than following the Mendelian law of random assortment. Changes in linkage groups can be caused by different processes which are further described in section 7.4.0.

There are four linkage groups in Drosophila, corresponding to the number of chromosomes. Wing length and body color are generally inherited together because the genes for these traits are on the same chromosome.

Morgan noted that mating commonly occurring wild-type flies having a grayish body and long wings with mutant flies having black bodies and short wings, resulted in a wild-type F1 generation. If a hybrid female is mated with a homozygous mutant male, 50% would be expected to be of wild-type, according to Mendelian genetics. Instead, 8.5 percent of the flies were black with vestigial wings, and 8.5 percent were gray with long wings.