A review of polygenic inheritance

1. A review of polygenic inheritance

2. Global Patterns of Human Variation • Can be examined genetically • Can be examined phenotypically • Are phenotypic differences concordant with genetic differences?

3. Eight classes of genetic similarity enzyme & blood group loci Arrayed by increasing difference Distribution of eight classes of skin pigmentation intensity Concordance or discordance?

4. However, there IS geographic structuring of allele frequencies. • Genetic distance map • 42 native human populations • Frequencies of 120 different alleles • Closer proximity in graph = greater genetic similarity • Related to geographic distances among the groups. • PPPPPopu Population differences

5. Average genetic differences Distance curtails gene flow among groups

6. Populational differences among human groups • Today, human races are distinguished by ethnic differences – NOT by biological differences. • Differences in culture • nationality • language • religion • Biologically, there is no Jewish race, no African race, no African-American race, etc. • But, biological differences may still be emphasized, even in sociology; e.g., people of color.

7. Effects of gene flow on populationse.g., microevolution in Ireland • Data set: anthropometric (skull) measurements • Collected in 1930s • >7000 men from 30 of 31 counties • Phenotypic measurements converted into similarity measurements: genetic distances • Plot of distances between samples from 30 counties. • Graphical pattern reveals the pattern of variation.

8. Prediction: because of location, the four centrally located counties should be genetically similar to all of the other counties • In a central position re of past migration routes and gene flow

9. M counties displaced away from the other counties H1: resulted from gene flow from Danish and Norwegian Viking invaders. One incursion Into; central Ireland involved 12,000 men.

10. Testing the hypothesis