Basic concepts of population genetics - Bioversity International

More documents

Recommendations

Info

Applying the 2 test: An example Genotype AA Aa aa No. observed 169 520 311 No. expected 250 500 250 X 2 calculation (169-250-0.5) 2 /250 (520-500-0.5) 2 /500 (311-250-0.5) 2 /250 X 2 value +25.921 +0.760 +14.641 41.322 = 0.05 Copyright: IPGRI and Cornell University, 2003 Population genetics 20 20 Decision criteria: 2 cal (41.322) > 2 tab (3.8) H 0 is rejected In this example, let’s say that allele frequencies were 0.429 for A 1 and 0.571 for A 2 . Each genotypic class was represented as in the table on the slide above. The hypotheses being tested are: H 0 = this population is in H-W equilibrium for its allele frequencies H a = this population is not in H-W equilibrium for its allele frequencies Because the number of genotypic classes is 3 and we therefore have only 1 degree of freedom, we apply the correction factor in our calculation of the 2 elements. The 2 calculated is 41.322. With this figure and with an error margin of 0.05%, the statistical evidence rejects H 0 , which means that this population is not in H-W equilibrium for the trait under study.
Calculating allele frequencies: Examples Calculating allele frequencies with a codominant marker Calculating allele frequencies with a dominant marker Calculating the allele frequencies with a codominant gene having multiple alleles Copyright: IPGRI and Cornell University, 2003 Population genetics 21 In the next few slides we show examples of calculations of allele frequencies for results obtained with different marker types. The examples are given with figures that emulate real gels and the bands obtained through the application of molecular markers. For details on molecular marker technologies and the interpretation of bands, see the training module Using Molecular Marker Technology in Studies on Plant Genetic Diversity (http://www.ipgri.cgiar.org/publications/pubfile.asp?ID_PUB=912). 21
Page 1 and 2: Genetic diversity analysis with mol
Page 3 and 4: Definitions: Population genetics T
Page 5 and 6: Phenotypic variation Pink Pale crea
Page 7 and 8: Genotype is … The description of
Page 9 and 10: What is polymorphism? ‘Presence
Page 11 and 12: Population structure Three levels o
Page 13 and 14: Allele frequency Allele frequency
Page 15 and 16: Genotype frequency This is the fre
Page 17 and 18: Demonstrating the H-W principle Gen
Page 19: The chi-square test This hypothesi
Page 23 and 24: Locus A B D … with a codominant m
Page 25 and 26: Locus A Locus B Locus D … with a
Page 27 and 28: ... with a codominant gene having m
Page 29 and 30: Random mating Mating that takes pl
Page 31 and 32: Inbreeding coefficient It compares
Page 33 and 34: Forces shaping genetic diversity M
Page 35 and 36: Migration It is the movement of in
Page 37 and 38: Selection It is the inherited abili
Page 39 and 40: Effective population size Ne is th
Page 41 and 42: Consequences … (continued) A bot
Page 43 and 44: Appendix 1 Copyright: IPGRI and Cor
Page 45 and 46: By now you should know … The bas
Page 47:
Next Measures of genetic diversity
show all

Basic concepts of population genetics - Bioversity International

Create successful ePaper yourself

Delete template?

Save as template?