BIOL 115 Lecture 1: 15-Summary of BIOL 112, 2010
25 Jun 2016
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Ratios the importance of ploidy: odd-n tend to be sterile - work for mitosis, but meiosis doesn"t work one homolog must go unpaired on the metaphase plate. Some haploids (yeast, molds, mosses, ferns) still work. Use diploids (embryos) to make more haploids through meiosis. Even-n work well for both mitosis and meiosis. 4n similar to 2n, just tend to be bigger trisomy slightly odd, 2n with extra like downs. Mendel: used discrete traits, used easily controlled crosses, used a trait that bred true (wrinkled always gave wrinkled, smooth, smooth) Found some traits are recessive and some are dominant: discovered, heredity exists as discrete units (alleles of genes, units do not blend in heterozygote. Segregation of the alleles into gametes and re-association in progeny explains the ratios of phenotypes: alleles of different genes also segregate (assort) 30 years later, meiosis confirmed the division of these alleles.
