General Genetics/Mendelian Inheritance
Gregor Johann Mendel was a monk in the Augustinian Monastery in the Brunn, Czech Republic. In 1854 he began the experiments which started modern genetics. His work with garden peas, Pisum sativum, was vital to our understanding of inheritance. He is known as the Father Of Genetics.
Mendel's Experiment 
Mendel's first step was breeding pure breeding strains of peas. The traits he studied included:
- Pea colour
- Height of pea plants
- and whether the Peas were wrinkled or smooth.
Mendel crossed the pure breeding Parental Generation (designated P). He found that the first generation (F1) was exclusively phenotypically one of the parental types. Mendel then crossed his F1 generation with itself. He found that the F2 generation showed a surprising trait, three quarters were like the F1 generation, while the remaining quarter were like the other Parents.
From this Mendel realised that there were two versions of each loci, one of which expressed dominance over the other. He called this Biparticulate Inheritance. If a gene was following this 3:1 pattern it was said to be segregating Normally.
By looking at multiple genes, Mendel showed that they were not linked to each other and that each loci he studied had no influence over the others. He called this Independent assortment.
By studying cases where the Mendelian laws we can also learn a lot. For instance, if a gene isn't segregating normally it may be sex linked. If two genes aren't Assorting Independently they're probably on the same chromosome
Mendel's laws are the first step to understanding Genetics, they lay down the basic concept of inheritance.