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Genetics and Human variation. Nick Martin Queensland Institute of Medical Research High Schools lecture: April 4, 2006. Individual differences. Physical attributes (height, eye color) Disease susceptibility (asthma, anxiety) Behavior (intelligence, personality)
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Genetics and Human variation Nick Martin Queensland Institute of Medical Research High Schools lecture: April 4, 2006
Individual differences • Physical attributes (height, eye color) • Disease susceptibility (asthma, anxiety) • Behavior (intelligence, personality) • Life outcomes (income, children)
Genetic Epidemiology • Establishing the role of genes and environment in variation in disease and complex traits • Finding those genes
3 Stages of Genetic Mapping • Are there genes influencing this trait? • Genetic epidemiological studies • Where are those genes? • Linkage analysis • What are those genes? • Association analysis
MZ and DZ twins: determining zygosity using ABI Profiler™ genotyping (8 STR markers + sex) Zygosity Determination • Identity at marker loci - except for rare mutation MZ DZ DZ
Total mole count for MZ and DZ twins MZ twins - 153 pairs, r = 0.94 DZ twins - 199 pairs, r = 0.60 400 400 300 300 Twin 1 Twin 1 200 200 100 100 0 0 0 100 200 300 400 0 100 200 300 400 Twin 2 Twin 2
ACE Model for twin data 1 MZ=1.0 / DZ=0.5 E C A A C E e c a a c e PT1 PT2
Sources of variation in QCST results Non-shared environment Additive genetic Shared environment
Are there common genetic and environmental factors influencing Verbal IQ, Performance IQ and QCST results? A1 A2 C1 .43 .66 .79 .48 .74 .41 VIQ PIQ QCST .34 .43 .53 E1 E2 E3
3 Stages of Genetic Mapping • Are there genes influencing this trait? • Epidemiological studies • Where are those genes? • Linkage analysis • What are those genes? • Association analysis
Genetics of asthma DPP10 GPRA EHF, ELF5 (11p13) FCER1B PHF11 ADAM33 1 9 10 11 12 13 21 22 X Y 2 14 15 16 17 18 19 20 3 4 5 6 7 8 Replicated regions @ p<0.01 (LOD>1.2) – Ober et al. (2000) Positionally cloned genes EHF and ELF5 (11p13) not replicated
Linkage = Co-segregation A3A4 A1A2 A1A3 A2A4 A2A3 Marker allele A1 cosegregates with dominant disease A1A2 A1A4 A3A4 A3A2
Human OCA2 and eye colour Zhu et al., Twins Res 7:197-210 (2004)
First genome-wide linkage scan for Intelligence Posthuma et al., AJHG, in press
3 Stages of Genetic Mapping • Are there genes influencing this trait? • Epidemiological studies • Where are those genes? • Linkage analysis • What are those genes? • Association analysis
First (unequivocal) positional cloning of a complex disease QTL !
Discordant caudal duplication in MZ twins 3 4 5 6 7 11 8 9 10 1 2 LTR Axin CpG Island Emma Whitelaw, Suyinn Chong Department of Biochemistry University of Sydney 308 bp 181 bp Twin 1- unaffected < Twin 2 - affected > Controls [e.g.]
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