Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I even say who wrote them. If you have more recent summaries to add to this collection, send them my way I guess. Sorry for the ads; they cover the costs of keeping this online.
Mendel. 1865. Experiments in plant hybridization. On course CD, from a web site, www.netspace.org/MendelWeb.
Observed: shape of peas, color of peas, color of seed-coat, form of ripe pods, color of unripe pods, position of flowers, length of stem.
Discusses risk of foreign pollination in section (3).
Observes that hybrids are not an average of the two parents: they reflect only the "dominant" traits, often mostly from on of the parents. Dominant traits are observed 3:1 relative to recessive traits in the first generation (of seeds that sprouted into plants). Of those with the dominant character in the first generation, 1:2 showed dominant traits in the second generation. Thus, by looking at the second generation, we see that the first generation had a 2:1:1 breakdown: 2 hybrids, one purely dominant, one purely recessive. Thus, the first generation had 2*Aa, one AA, and one aa. (He's doing what Green and Gerber 2002 called a downstream experiment).
He first did this with plants differing on a single trait, then on plants differing on multiple traits.
Research on similar subjects