Variations on Mendel After Mendel's results were rediscovered in 1900 researchers began to notice unusual inheritance patterns. While much research continued using plant systems such as Mendel's peas, researchers started to extend the studies to other organisms. In particular, T. H. Morgan's use of the fruit fly, Drosophila melanogaster, greatly sped up the pace of the research. Morgan chose to work on the fruit fly because their small size (100s can be kept in a small bottle), rapid generation time (two weeks from egg to adult) and numerous physical features (over 3,000 phenotypes have been characterized) made them ideal for carrying out numerous crosses with large sample sizes. There are many deviations from simple mendelian genetics caused by how the alleles determine the phenotype. As there is usually a large number of steps between the DNA sequence of the allele and the phenotype finally produced (DNA to RNA to protein to cellular characteristic to balding head, for instance) many complications are possible. Some of the more common ones are allelic effects (multiple alleles, incomplete domianance, epistasis, etc.), sex effects, environmental effects, genomic effects and additive genes. Bell CSU Chico Library This document is copyright of Jeff Bell Last Update: Wednesday, August 12, 1998