Genetics

http://www.bbc.co.uk/schools/gcsebitesize/science/21c/genetics/genesinheritencerev1.shtml

Mendel noted flower color and position, stem length, seed shape and color, and pod shape and color. To keep this post simple, we’ll focus only on seed shape.

In the first generation (F0), Mendel crossed a purebred plant with wrinkled peas with a purebred plant with smooth peas. The resultant progeny (F1 generation) all had smooth peas. Upon allowing that F1 to self-pollinate, the wrinkled pea trait reemerged in F2, though smooth peas were still the most common, by a ratio of 3:1. These observations led Mendel to two important principles: the law of segregation, and the law of independent assortment.

The law of segregation states that each parent has two versions of a trait to pass on (known as an allele). Random chance determines which alleles get passed on.

The law of independent assortment states that different alleles get passed independently from each other. That is, seed shape has nothing to do with flower color, which is also independent from stem length. While linkage does exist, alleles on different chromosomes will be passed on independently.

While Mendel is now hailed as the father of all genetics, his initial publication in 1866 went largely unnoticed until the early 1900s, after his death.

For more information: http://anthro.palomar.edu/mendel/mendel_1.htm