Announcements Recitation reminders o Human adaptation assignment sign up for an article through the doodle polls sent out o Make a prezi account o Bring a laptop tablet to recitation Lecture o MIDTERM on Feb 24 o Review sheet will be up by this weekend Review Mutation Gene Flow Genetic Drift Natural Selection Differential survival and reproduction of some organisms over others because of their biological characteristics Population Growth The Evolutionary Forces o Interaction of the Evolutionary Forces o The four evolutionary forces mutation natural selection genetic drift and gene flow sometimes act together and sometimes act in opposition o Different evolutionary forces can produce the same or opposite effects Their exact interaction depends on a wide variety of factors biochemical and physical effects of different alleles presence absence of dominance population size etc Slide 4 NATURAL SELECTION IN HUMAN POPULATIONS Chapter 15 Summary Natural Selection and Disease Natural Selection and Skin Color Natural Selection and Culture Change Sickle Cell Anemia o A genetic disease in which the red blood cells are twisted in shape and may painfully block circulation o This often leads to medical crises and may cause an early death o The recessive disease occurs in children who have inherited the mutated gene from BOTH their parents mostly among people of African or Mediterranean origin Sickle Cell Anemia How it Works o Each individual has two genes at any given locus o They can be the same allele homozygous or different alleles heterozygous o HbA HbA Normal o HbA HbS Carrier of the trait o HbS HbS Sickle Cell Anemia 2 10 2014 1 Malaria Plasmodium falciparum Why is HbS so frequent especially if HbS HbS individuals die selected out Natural Selection In a Malarial Environment o Malaria is a great example of Natural Selection operating on the evolution of humans o Remember evolution is any change in allele gene frequency o HbA HbA Die from malaria o HbA HbS Survive malaria o HbS HbS Die from anemia HbA HbS Heterozygote HbA HbS Heterozygote 2 10 2014 2 Deprived of Potassium the Parasite Dies Malaria Sickle Cell Sickle Cell Horticulture and the Sickle Cell Allele in Africa Prior to the development of horticulture in Africa the frequency of the sickle cell allele was probably low It was an evolutionary advantage initially with the increase of malaria Cultural adaptations ecology of other organisms mosquitoes and malaria parasite causing genetic change in the human population NOW LET S SEE IT IN ACTION Natural Selection Model In a Malarial Environment Selection in the Malarial Environment Genotype Fitness Selection Coef HbA HbA 0 7961 0 2039 HbA HbS 1 000 0 000 HbS HbS 0 1698 0 8302 p s s t and q t s t HbA 0 8302 8302 0 2039 0 8028 HbS 0 2039 0 2039 0 8302 0 1963 2 10 2014 HbA HbS 3 00 10 20 30 40 50 60 70 80 91234567891011frequencygenerationChange in Allele Frequency After 10 generationsF p F q o What type of selection is working on Sickle Cell Anemia o Hemoglobin Sickle Cell and Malaria Selection o Both Balancing and Stabilizing Selection operate to maintain variation in a population Natural Selection in Human Populations o Distribution of the Sickle Cell Allele and Malaria o The most widely studied mutations include the hemoglobin S allele known as the sickle cell allele o Mutation introduces is but natural selection eliminates it o The distribution of the allele is related to the prevalence of certain forms of malaria and is caused by a virus or parasite o A person who has two S alleles has sickle cell anemia o The evolution of the S Allele o In a malarial environment heterozygous people have an advantage o Equilibrium is one in which the fitness of the entire population is at a o The cost of adaptation however is an increased proportion of individuals maximum with sickle cell anemia Why Do We Care Polymorphism Genetic locus with 2 or more alleles in appreciable frequency Appreciable about 1 1 100 Higher than mutation alone about 1 10 000 Evolutionary explanation Why Study Blood Polymorphisms Antigen o Easy to get and transport o Phenotypic expression unaffected by environment o Simple Mendelian Traits oA molecule organic or inorganic that can provoke the immune system to produce antibodies Dust Antigen Foreign Invader Pollen Microbes 2 10 2014 4 Polymorphism5 7 15 15 18 25 80 75 60 0 10 20 30 40 50 60 70 80 90 100 Population1Population2Population3PopulationFrequencyType 0Type BType A Antibody oProteins in the blood that bind to foreign antigen molecules rendering them harmless oAntibodies form in response to antigens Antibody Army Landsteiner 1900 o During 19th century conflicts battlefield blood transfusions were attempted o Severe reactions including agglutination below kidney failure and death o If antigen is on cell surface the antibody may react by causing clumping Blood Groups CONVENTIONAL NAME ISBT SYMBOL ISBT NUMBER ANTIGENS BLOOD GROUP SYSTEMS ABO MNS P1 RH LU KEL LE FY JK DI YT XG SC DO CO LW H XK GE KN IN OK RAPH JMH 001 002 003 004 005 006 007 008 009 010 011 012 013 014 015 016 017 018 019 020 021 022 023 024 025 026 4 37 1 47 18 21 3 6 3 2 2 1 3 5 3 3 9 1 1 7 5 2 Landsteiner Wiener Chido Rogers CH RG CROMER 10 Lutheran ABO MNSs P Rh Kell Lewis Duffy Kidd Diego Cartwright Xg Scianna Dombrock Colton Hh Kx Gerbich Cromer Knops Indian Ok Raph JMH 26 Systems present on the surface of the RBC Blood Type oWe must recognize something as self oDifferent blood groups are identified by the antigen oEach system has its own antigen antibody reaction o When an individuals blood is exposed to anti A antibodies it clumps o It does not clump when exposed to anti B antibodies o The individual must be Type A their A antigen provoked an immune response by the anti A antibodies The ABO System ABO locus on Chromosome 9 Blood type is expressed through antigens ABO Phenotype Genotyp Antigens Antibodi s A B AB O es AA AO BB BO AB OO A B A B None es Anti B Anti A None Anti A Anti B ABO antibodies are naturally occurring A and B are Codominant and O is recessive O is the Universal Donor Who is the Universal Recipient 2 10 2014 5 Anthropology and ABO Why Why is the ABO polymorphism maintained in Humans Why do ABO frequencies differ between populations Distribution of Type B Distribution of Type A O 62 5 A 21 5 B 16 Distribution of Type O Founder Effect Natural Selection High frequencies of type O in relatively isolated populations e g Australia and the Americas Smallpox Type A and Type AB Bubonic