Mendel first began the study of heredity in 1857 using common garden peas (Mendelian, 2003). He conducted controlled mating experiments looking at two variants of seven different traits, including plant size, pod color, and fruit shape and color, and from his results, developed two principles which became the two Principles of Mendelian Inheritance. The two principles are: 1) the Principle of Segregation - members of a given pair of alleles segregate from each other in the same manner as homologous chromosomes separate from each other in meiosis to form germ cells; and 2) the Principle of Independent Assortment - a given pair of alleles assort independently with respect to any other allele pair on a non-homologous chromosome during germ cell formation. This suggested that traits were transmitted between generations in a predictable manner, and that the gene for each trait could exist in two alternate forms, which resulted in phenotypes. Plants such as the garden pea are useful tools in the study of genetics to look at inherited characteristics.
The fruit fly Drosophila melanogaster was first used in 1900 as a useful tool in genetic studies of diploid organisms because it has a short life-cycle, is easily handled and bred, and produces many progeny from a single mating (Mendelian, 2003). It also has a large polytene chromosome in the salivary gland of the third-instar larval stage, which can be used for cytological studies of chromosome aberrations. Many mutant forms of Drosophila exist, with differences in eye shape and color, wing size and shape, body color, etc., which are useful for looking at inheritance patterns. These mutant strains can be used in genetic studies such as the experiment described in this paper.
Mice are also used frequently as genetic models. Like Drosophila, they breed rapidly and profusely, and can be easily handled easily in the laboratory. They are small enough to be housed in large numbers i...