BISC 202 Lecture Notes - Lecture 3: Gamete, Zygosity, Design Of Experiments
8 Oct 2017
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Me(cid:374)del(cid:859)s e(cid:454)peri(cid:373)e(cid:374)tal approa(cid:272)h (cid:894)~(cid:1005)(cid:1012)(cid:1009)(cid:1010)-1868): chose appropriate experimental organism, selected phenotypes that displayed discontinuous variation, carefully designed experiments, collected data (counted phenotypic classes, formulated hypotheses and made predictions, designed and carried out new experiments to test hypotheses/predictions. This first result led mendel to characterize some phenotypes as dominant and others as recessive. Here, the yellow is dominant, because all the f1 progeny show the trait. The green is recessive; in combination with yellow, green cannot be seen. The most important thing mendel did was to count the f2 progeny, and observe that there was a 3:1 ratio of dominant:recessive. He observed this same 3:1 ratio for all of the traits that he studied. Me(cid:374)del(cid:859)s third postulate: duri(cid:374)g the for(cid:373)atio(cid:374) of ga(cid:373)etes, the paired u(cid:374)it fa(cid:272)tors separate (cid:894)segregate(cid:895) such that each gamete receives only one at random. Diploid crosses- segregation ratios genotypic and phenotypic characteristic of single-gene inheritance: three possi(cid:271)le diploid ge(cid:374)ot(cid:455)pes a/a ; a/a ; a/a, ix possible diploid crosses.
