ANT203H5 Chapter Notes - Chapter 14: Intelligence Quotient, Heritability, Negroid

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25 Apr 2012
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Chapter 14 Study of Human Variation
-the least amount of variation - the most amount of variation (existing in humans)
1) physical characteristics (ex. hair colour)
2) less observed characteristics (teeth)
3) Variation at the molecular level
3 common questions to ask when looking at human variation:
1) what is the pattern of variation WITHIN a population?
- allele frequencies, what are genotypes and phenotypes = simple traits
- what is the average value, and the range around this average value = complex traits
2) what is the pattern of variation BETWEEN populations?
- do allele freq differ across populations?
3) why are there patterns of variation?
*biological anthropologists study variation in terms of evolutionary forces and biocultural
adaptations
* but individuals often discuss variation as RACE and ETHNICITY
- people tend to classify and reduce variation by using averages or stereotypes
2 goals of this chapter:
1) look at different types of variation
2) look at the global patterns of human genetic diversity
Measuring human variation
Variation: differences existing among people and populations
- can exist in terms of physical traits but also in terms of biochemical traits ex. diff blood
groups (A, B, O, AB)
- can’t just look at physical observable traits because its 1) subjective what u think is tall may
be diff from someone else’s perspective
2) our categories of variation don’t show that traits are continous – ex. skin colour isn’t discrete
categories, it is continuous
3) a lot of variation that exists cant be seen by observing
Red blood cell polymorphism
- a lot of info has been found about genetic traits by looking at red blood cells
- RBC polymorphism include blood types and protein and enzyme types
Polymorphism = genetic trait where at least 2 alleles have a frequency greater than 1%
Blood type
- different blood group systems have been found based on the types of molecules present on the
surface of the red blood cells ex. ABO blood type, MN blood type, Rhesus, Diego, Duffy and
Kell blood group systems
- different blood groups are identified based on different antibody-antigen reaction
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- antibody= substances that react to foreign substances
Antigen = substance invading the body which can stimulate production of antibodies
- ex. AB blood group
Has 3 alleles A, B, O where A and B are codominant, O is recessive
- anti-A (antibody) reacts to antigens A and AB
- if blood clumps to anti A antibodies but not B antibodies it means that the person has type A
blood
Blood proteins and enzymes
- genotypes for blood proteins and enzymes is found using a method called electrophoresis: lab
technique electric current seperates proteins thus genotype can be determined
- NEGATIVE (electricity flows ) POSITIVE
Blood cells also moves
* all occurs in a gel
*thus proteins fromm the blood move with electrons at faster and slower rates - the distance
they travel through the gel = determines genotype
*diagram pg 361 shows same thing
HLA system = human leukocyte antigen system
- variation in antigens are found on the surface of white blood cells = leukocytes
- controlled by loci on chromosome 6
- important in bodys autoimmune response HLA types determines if organ transplant would be
successful
- there are a lot of differences in HLA allele frequencies among human populations good
marker to see genetic similarity patterns
- HLA antigens also associated with diseases like arthritis
DNA ANALYSIS
- with cheek swabs or hair sample can see forms of variation by looking at DNA sequences
Methods of DNA analysis
- sources of variation:
1) RFLPs = Restriction fragment length polymorphisms differences in the length of DNA
fragments give a useful measure of human variation @ the molecular level
- thus it’s a genetic trait produced when certain enzymes cut the DNA sequence into different
DNA fragment lengths
2) looking at non coding DNA sequences that are repeated = microsatellite DNA
- short repeated sections of DNA (2-5 bases) number of repeats is variable
- also called short tandem repeats STR
- ex. 5 repeats of CA CACACACACA
*long repeated unit of DNA = minisatellite
3) Alu insertion a sequence of DNA repeated at different locations on different chromosomes
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