《人口与资源英》PPT课件.ppt

POPULATION GENETICS, 2008 Paul Billiet ODWS,Predictable patterns of inheritance in a population so long as,the population is large enough not to show the effects of a random loss of genes by chance events i.e. there is no genetic drift the mutation rate at the locus of the gene being studied is not significantly high mating between individuals is random (a panmictic population) new individuals are not gained by immigration or lost be emigration i.e. there is no gene flow between neighbouring populations the genes allele has no selective advantage or disadvantage, 2008 Paul Billiet ODWS, 衬塑复合管 涂塑复合管 钢塑复合管 消防涂覆钢管,SUMMARY,Genetic drift Mutation Mating choice Migration Natural selection,All can affect the transmission of genes from generation to generation,Genetic Equilibrium If none of these factors is operating then the relative proportions of the alleles (the GENE FREQUENCIES) will be constant, 2008 Paul Billiet ODWS,THE HARDY WEINBERG PRINCIPLE,Step 1 Calculating the gene frequencies from the genotype frequencies Easily done for codominant alleles (each genotype has a different phenotype), 2008 Paul Billiet ODWS,Iceland,Population 313 337 (2007 est) Area 103 000 km2 Distance from mainland Europe 970 km, 2008 Paul Billiet ODWS,Google Earth,Example Icelandic population: The MN blood group, 2008 Paul Billiet ODWS,MN blood group in Iceland,Total Mm alleles = (2 x 233) + (1 x 385) = 851 Total Mn alleles = (2 x 129) + (1 x 385) = 643 Total of both alleles =1494 = 2 x 747 (humans are diploid organisms) Frequency of the Mm allele = 851/1494 = 0.57 or 57% Frequency of the Mn allele = 643/1494 = 0.43 or 43%, 2008 Paul Billiet ODWS,In general for a diallellic gene A and a (or Ax and Ay),If the frequency of t