Brief History of Genetics • 8000 to 1000 BC horses, camels, and wolves domesticated for human use • Bred for strength, speed, agility, intelligence • Early selective breeding: domesticated wolves • Humans and wolves were aggressive • Friendly wolves caught food from humans, when humans gave them food friendship occurred • Now over 400 dog breads from selective breedings • Used traits for hunting/tracking, heading, guarding etc • William Harvey- 1600z • Epigenesis: fertilized human egg undergoes speci c developmental events that lead to formation of human • Cell divides and divides • Contradicted preformation • Preformation: fertilized egg contains tiny version of completely developed adult (or preformation) • Homunculus: the name for the completely developed adult in the egg • Cell Theory (correct theory) • Introduced by Matthias Schleiden and Theodor Schwan • All living organisms are composed of organized structures called cells and the cells came from identical precursor cells • Fundamental biological fact • Debunked spontaneous generation or when living things could spontaneously generate from nonliving components • Thought ees come from dust, or from mud of rivers • Charles Darwin 1859 • Published Origin of Species • Postulated theory of natural selection: more o springs produced than the environment can support • Survival in the crowded environments leads to struggle in the population so o spring with most desirable traits survives • Overtime variations in o springs evolve making them more adaptive and eventually new species could evolve • Gregor Mendel • Experiment with pea plants to see how traits are inherited from generation to generation • Did not de ne heredity rule but explain development of hybrids • Results explain trait transmission • Example in modern: gene from digesting lactose • Humans stop making lactase (enzyme for milk digestion) when stoping breastfeeding • Mutation arose from people drinking animal milk fi ff ff fi fl ff Genes in the Transmission of Traits and Genetic Variation • Genetics: study of heredity • Modern genetics: study of heredity
