《人口與資源英》PPT課件

1、POPULATION GENETICS 2008 Paul Billiet ODWS Predictable patterns of inheritance in a population so long as nthe 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 nthe mutation rate at the locus of the gene being studied is not

2、 significantly high nmating between individuals is random (a panmictic population) nnew individuals are not gained by immigration or lost be emigration i.e. there is no gene flow between neighbouring populations nthe genes allele has no selective advantage or disadvantage 2008 Paul Billiet ODWS http

3、:/ 襯塑復(fù)合管 涂塑復(fù)合管 鋼塑復(fù)合管 消防涂覆鋼管 SUMMARY nGenetic drift nMutation nMating choice nMigration nNatural 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 FREQUENCIE

4、S) will be constant 2008 Paul Billiet ODWS THE HARDY WEINBERG PRINCIPLE Step 1 nCalculating the gene frequencies from the genotype frequencies nEasily done for codominant alleles (each genotype has a different phenotype) 2008 Paul Billiet ODWS Iceland Population n313 337 (2007 est) Area n103 000 km2

5、 Distance from mainland Europe n970 km 2008 Paul Billiet ODWS Google Earth Example Icelandic population: The MN blood group 2 Mn alleles per person 1 Mn allele per person 1 Mm allele per person 2 Mm alleles per person Contribution to gene pool 129385233Numbers747 MnMnMmMnMmMmGenotypes Type NType MNT

6、ype MPhenotypesSample Population 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 fr