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Species and Races Ch. 12.2 – 12.3

Species and Races Ch. 12.2 – 12.3. Lecture 16 Tuesday, April 9, 2013. BiSc 001 Spring 2013 Guest Lecture Dr. Jihye Park. Modern Humans: A History. Immediate predecessor of Homo sapiens was Homo erectus. H. erectus first appears in fossil record ~1. 8 MYA

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Species and Races Ch. 12.2 – 12.3

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  1. Species and RacesCh. 12.2 – 12.3 Lecture 16 Tuesday, April 9, 2013 BiSc 001 Spring 2013 Guest Lecture Dr. Jihye Park

  2. Modern Humans: A History • Immediate predecessorofHomo sapienswasHomo erectus • H. erectus first appears in fossil record ~1.8 MYA • H. sapiens first appears in fossil record ~250,000 years ago http://www.naturalclimatechange.us/Large%20Images/IMG_0008.jpg

  3. Modern Humans: Out of Africa • ModernhumansdescendedfromAfricanancestorswithin the last 200,000 years. • Humanpopulations in Africa havegreatestgeneticdiversity. http://newswatch.nationalgeographic.com/2011/11/03/modern-humans-wandered-out-of-africa-via-arabia/

  4. Allele frequency • Evolutionresults in a change in allele frequency. • Allele frequency: the percentageof the gene copies in a populationthat are of a particularform (allele) • If a race isisolatedfromotherraces, there are twoexpectations: • Some allelesuniqueto the race • Differences in allele frequencycomparedtootherraces

  5. Hardy-Weinberg Theorem • Allele frequencieswillremainstable in populationsthatmeetconditions: • Largesize • Randommating • No migration • No naturalselection http://www.kindgreenbuds.com/images/hardy-weinberg-2.jpg

  6. Hardy-Weinberg Theorem • HW Theoremisexpressedasanequation • p2 + 2pq + q2 = 1 • p and q are allelesof a gene • p2 and q2 are homozygouscondition (i.e. AA or aa) • 2pqisheterozygouscondition (i.e. Aa) http://lakesideblogs.com/aparrott/Hardy-Weinberg_Human_gametes.gif

  7. Hardy-Weinberg Theorem

  8. Hardy-Weinberg Theorem

  9. Hardy-Weinberg Theorem • 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. Hardy-Weinberg Theorem • 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. Hardy-Weinberg Theorem • 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. Hardy-Weinberg Theorem • 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 = 0.22 = 0.04 • The frequency of genotype Yy • 2*0.2*0.8 = 0.32 • The frequency of genotype yy • 0.82 = 0.64 • Check! 0.04 + 0.32 + 0.64 = 1

  13. Human Genome Project • No uniquealleles are found in allmembersofone race. • Single nucelotidepolymorphisms (SNPs) are single base pair in a DNA sequencethat can differfromoneinidvidualtoanother. • 99% ofhumangenomeis the same, the 1% are primarilymadeofSNPs. http://www.nature.com/nature/focus/1000genomes/images/main_bg.jpg

  14. Human races are not isolated biological groups • Sicklecell allele • Cysticfibrosis allele http://geneed.nlm.nih.gov/images/sickle_cell_disease_sm.jpg

  15. Human races are not isolated biological groups • The allele distributionof3traitsthat do not cluster based on “race.”

  16. Human races have never been truly isolated • The movementofallelesfromAsianpopulationsintoEuropeanpopulations.

  17. Why Human Groups Differ? • Natural Selection • Convergent Evolution • Genetic Drift • Sexual Selection • Assortative Mating http://2.bp.blogspot.com/-gQ3XyGA38bI/UEZGWacqS9I/AAAAAAAAABg/w2YK7ZVIR5g/s1600/diversity2.jpg

  18. Natural selection • Sicklecell allele ishigher in populationsthat are malaria-prone. • Noseshapeiscorrelatedwithclimatefactors.

  19. Convergent evolution • Traitssharedbyunrelatedpopulationsdue tosimilaritiesofenvironment • Strong correlationbetweenskin color and exposureto UV light

  20. Convergent evolution • Effectsof UV levels on fitness

  21. Genetic drift • Change in allele frequencythatoccurs due to chance • Humans are highly mobile • Smallgroupscolonizingnewareas are prone togeneticdrift http://www.hdwallpapersfull.com/wallpapers/ice-age-4-continental-drift--1920x1200.jpg

  22. Genetic drift • Foundereffect–geneticdifferencesresultingfrom a small sample

  23. Genetic drift • Populationbottleneck–geneticchangeresultingfrom a dramaticreductionofpopulationnumbers

  24. Genetic drift • Chance events–smallpopulations are especially prone to loss ofallelesthrough chance

  25. Sexual selection • When a trait influences chance ofmating • Sexualselectionoftenaccountsfor male/femaledifferences in manyanimalspecies

  26. Assortative Mating • Tendencyoforganismtochoose mate thatresembles self • People tendto mate assortativelybyheight or skin color • Positive assortativematingtendstoexaggeratedifferencesbetweengroups http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/K/Koren.jpg

  27. You should know by now! • 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 assortativemating with examples!

  28. We are still the same!!! http://www.colourbox.com/preview/6466924-613405-3d-illustration-social-media-group-of-different-people-around-the-earth.jpg

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