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Biology Unit 2

Population Genetics

QuestionAnswer
Gene pool all of the genes in a population. study genetic variation within gene pool and how variation changes from one generation to the next. emphasis on variation in alleles between members of a population
Snps single, nucleotide, polymorphism. smallest type of genetic change in a gene. most common= 90% of variation in a human gene sequence. Accidental switch. 3rd base-> little change. 2nd-> can alter greatly. 1st-> almost always diff amino acid
modern description of natural selection some alleles may encode proteins that enhance an individuals survival or reproductive success compared to that of other members of the population
N.s patterns. directional Preponderance of individual at one extreme of a phenotypic distribution that have a greater reproductive success. preferential selection of one extreme. pick off. Initiators: new allele introduced, prolonged environmental change
N.s patterns. stabilizing favours affect the survival of individuals with extreme characteristics--> preferential survival and reproduction of intermediate phenotypes. extreme values selected against.
N.s patterns. disruptive eliminate moderate phenotype. 2 or more diff genotypes which produce diff phenotypes
N.s patterns. balancing (like stabilizing). maintains genetic diversity. balanced polymorphism. two or more alleles kept in balance. 2 mechanims: 1.for a single gene, hereozygote favoured. 2. negative frequecy= dependent on selection. rare ind. = higher fitness.
Intrasexal selection vs intersexual intra:not sex,used to perpetuate the act. members of same sex. horns, antlers, compete for mating opportunities. inter: members of opp. sex. female choice. often results in showy characteristics for males.
Population growth. independent R. weather catastrophe, stochastic events. massive eruptions& crashes. small, short lived, variable environments, develop & mature quickly, large litters, exponential growth, reproduce early in life, little parent care. less mate choice. abiotic factors
population growth. dependent K. competition, predation. crowding&stress. more predicable events. large, long lived, stable environments, develop slowly, small litters, logistic growth, reproduce later in life, extended parent care, more mate choice. secondary sexual characteristics.
Random genetic drift changes in allelic frequency due to random sampling error. random events (initially) unrelated to fitness. favours either loss of or fixations of an allele. 0 or 100%. faster in small populations
bottle neck effect population reduced dramatically and then rebuilds. randomly eliminated members without regard to genotype less genetic variation
founders effect random sampling error. small group separates from large group. small founding population, allele frequencies in founding population may differ greatly from original.
Neutral theory of evolution Main idea-> modern variation in gene sequences is explained by neutral variation rather than adaptive radiation no effect on phenotype. non darwianian evolution: shift in gene but natural. neutral variation selection doesn't effect it. most genetic variation is due to accumulation of neutral mutations that have obtained high frequencies due to genetic drift.
Migration gene flow occurs when individuals migrate between populations having diff. allele frequencies. migration reduce differences in allele frequencies between the 2 populations. enhances genetic diversity in a population, disrupts gene flow.
Non random mating. Assortative, Dissassortative, Inbreeding A: individuals with similar phenotypes are more likely to mate. increase proportion of homo zygotes. D: dissimilar genotypes, favours heterozygous I: lower mean fitness of pop, in breeding depression
Created by: bdinney22
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