1. Lecture 16 Tuesday, April 9, 2013 BiSc 001 Spring 2013 Guest Lecture Dr. Jihye Park

2.  Immediate predecessor of Homo sapiens was Homo erectus http://www.naturalclimatechange.us/Large% 20Images/IMG_0008.jpg ◦ H. erectus first appears in fossil record ~1.8 MYA ◦ H. sapiens first appears in fossil record ~250,000 years ago

3.  Modern humans descended from African ancestors within the last 200,000 years. http://newswatch.nationalgeographic.com/ 2011/11/03/modern-humans-wandered- out-of-africa-via-arabia/ ◦ Human populations in Africa have greatest genetic diversity.

4.  Evolution results in a change in allele frequency. ◦ Allele frequency: the percentage of the gene copies in a population that are of a particular form (allele)  If a race is isolated from other races, there are two expectations: ◦ Some alleles unique to the race ◦ Differences in allele frequency compared to other races

5.  Allele frequencies will remain stable in populations that meet conditions: http://www.kindgreenbuds.com/images/har dy-weinberg-2.jpg ◦ Large size ◦ Random mating ◦ No migration ◦ No natural selection

6.  HW Theorem is expressed as an equation ◦ p 2 + 2pq + q 2 = 1 http://lakesideblogs.com/aparrott/Hardy- Weinberg_Human_gametes.gif ◦ p and q are alleles of a gene ◦ p 2 and q 2 are homozygous condition (i.e. AA or aa) ◦ 2pq is heterozygous condition (i.e. Aa)

9.  Cystic fibrosis, a recessive disease, affects 1 of every 2500 Caucasian babies born in the United States, a frequency of 0.0004. Use the Hardy-Weinberg theorem to calculate following frequencies in this population.  The frequency of the cystic fibrosis allele

10.  Cystic fibrosis, a recessive disease, affects 1 of every 2500 Caucasian babies born in the United States, a frequency of 0.0004. Use the Hardy-Weinberg theorem to calculate following frequencies in this population.  The frequency of the cystic fibrosis allele ◦ √0.0004 = 0.02

11.  The allele y occurs with a frequency of 0.8 in a population of clams. Give the frequency of genotypes YY, Yy, and yy.  The frequency of genotype YY  The frequency of genotype Yy  The frequency of genotype yy

12.  The allele y occurs with a frequency of 0.8 in a population of clams. Give the frequency of genotypes YY, Yy, and yy.  The frequency of genotype YY ◦ (1-0.8) 2 = 0.2 2 = 0.04  The frequency of genotype Yy ◦ 2*0.2*0.8 = 0.32  The frequency of genotype yy ◦ 0.8 2 = 0.64  Check! 0.04 + 0.32 + 0.64 = 1

13.  No unique alleles are found in all members of one race.  Single nucelotide polymorphisms (SNPs) are single base pair in a DNA sequence that can differ from one inidvidual to another.  99% of human genome is the same, the 1% are primarily made of SNPs. http://www.nature.com/nature/focus/1000 genomes/images/main_bg.jpg

14.  Sickle cell allele  Cystic fibrosis allele http://geneed.nlm.nih.gov/images/sickle_c ell_disease_sm.jpg

15.  The allele distribution of 3 traits that do not cluster based on “race.”

16.  The movement of alleles from Asian populations into European populations.

17.  Natural Selection  Convergent Evolution  Genetic Drift  Sexual Selection  Assortative Mating http://2.bp.blogspot.com/- gQ3XyGA38bI/UEZGWacqS9I/AAAAAAAAAB g/w2YK7ZVIR5g/s1600/diversity2.jpg

18.  Sickle cell allele is higher in populations that are malaria- prone.  Nose shape is correlated with climate factors.

19.  Traits shared by unrelated populations due to similarities of environment ◦ Strong correlation between skin color and exposure to UV light

20.  Effects of UV levels on fitness

21.  Change in allele frequency that occurs due to chance http://www.hdwallpapersfull.com/wallpaper s/ice-age-4-continental-drift-- 1920x1200.jpg ◦ Humans are highly mobile ◦ Small groups colonizing new areas are prone to genetic drift

22.  Founder effect – genetic differences resulting from a small sample

23.  Population bottleneck – genetic change resulting from a dramatic reduction of population numbers

24.  Chance events – small populations are especially prone to loss of alleles through chance

25.  When a trait influences chance of mating ◦ Sexual selection often accounts for male/female differences in many animal species

26.  Tendency of organism to choose mate that resembles self  People tend to mate assortatively by height or skin color  Positive assortative mating tends to exaggerate differences between groups http://users.rcn.com/jkimball.ma.ultranet/B iologyPages/K/Koren.jpg

27.  Modern human history  Allele frequency in populations  Hardy-Weinberg Theorem conditions and calculation  SNPs and human races are not isolated biological groups  Human groups are different due to natural selection, convergent evolution, genetic drift (founder effect, bottleneck effect, and by chance), sexual selection, and assortative mating with examples!

28. http://www.colourbox.com/preview/64669 24-613405-3d-illustration-social-media- group-of-different-people-around-the- earth.jpg