华中师范大学《遗传学》课件-第3章摩根和果蝇.pptxVIP

第三章 Morgan and Drosophila华中师范大学《遗传学》 One of Those Who Was Most Skeptical of Mendel was Embryologist T.H. MorganMorgan (1866-1945), at Columbia University was skeptical of all theories that postulated unseen elements:Morgan was interested in the problem of heredity, however, because he wanted to show that Darwin was wrong in believing that evolution occurred by slow, gradual change.So in 1908 he began breeding fruit flies. Morgan and his son at Woods Hole, 1907 Thomas Hunt Morgan, the first native-born American to win the Nobel Prize, founder of modern genetics Morgan et al. 1915“As will be shown now, certain factors follow the distribution of the X chromosome and are therefore supposed to be “contained in them.”Emphasis mine – fdu. ↓Genes lie on chromosomes Drosophila Was A Highly Useful Laboratory Organism Produces new generation in 12-15 daysEasy to keep in laboratoryProduces large number of offspring each generation Morgan and DrosophilaMorgan was not a geneticist by training (he was an embryologist), and he was not the first one to use Drosophila for purposes of genetic research (Castle was).“One of the baffling problems of breeders in pre-Mendelian days had been the effects of inbreeding and crossbreeding. What these were was a much-debated question. We set out to give it an experimental test and found ready to hand a rapidly breeding little fly, Drosophila, being cultured in the laboratory by a graduate student as embryological material. This, he told us, would complete a generation within a fortnight. (Charles Woodworth, prof entomology at UC Berkeley). … We began culturing the fly on pulped Concord grapes, but this gave us poor results as many of the larvae would get drowned and then our population statistics were no good. As grapes became out of season, we tried other fruits, and finally hit the jackpot in bananas. …The conclusion drawn [from our studies] was that inbreeding reduces very slightly the productiveness of Drosophila. … This was not a conclu