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Unformatted text preview: Reading Notes 20:22 Reading #1: Chapter 14 The gene idea is a particulate hypothesis of inheritance Parents pass on discrete heritable units that retain their separate identities in the offspring Character: a heritable feature that varies among individuals o Example: color Trait: each variant of a character Mendel used peas because of their short generation time and his ability to control their mating True breeding : Plants that over time produced only the same variety as the parent plant o Homozygous plants breed true Hybridization: The mating or crossing of two true-breeding varieties P-generation: The true-breeding parents/ parental generation F-1 generation: Hybrid offspring/ first filial generation F-2 generation: the generation resulting from the self-pollination of F1 hybrids Alleles: alternative versions of genes An organism inherits one allele from each parent If the two alleles at a locus differ, then the dominant allele determines the organisms appearance while the recessive allele has no noticeable effect Law of Segregation: The two alleles for a heritable character segregate during gamete formation and end up in different gametes Testcross: Breeding an organism of an unknown genotype with a recessive homozygote Monohybrids: heterozygous for one character Dihybrids: heterozygous for two characters Law of Independent Assortment: each pair of alleles segregates independently of other pairs of alleles during gamete formation Probability Rules To determine the probability that two or more independent events will occur together, multiply the probability of one event by the probability of the other. The probability that any one of two or more mutually exclusive events will occur is calculated by adding their individual probabilities Spectrum of Dominance Incomplete dominance: neither allele is completely dominant and the F1 hybrids have a phenotype somewhere between those of the parental varieties Codominance: The two alleles both affect the phenotype in separate, distinguishable ways Pleitropy: Refers to the fact that genes have multiple phenotypic effects Epistasis: A gene at one locus alters the phenotypic expression of a gene at a second locus Polygenic inheritance: An additive effect of two or more genes on a single phenotypic character Can be indicated by quantitative variation Reading #2: 15.1-15.3, 16.1 Chromosome Theory of Inheritance: Mendelian genes have specific loci along chromosomes, and it is the chromosomes that undergo segregation and...
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- Fall '07