Biological(BeginningsAnnouncements• Due$datesOutline• Genetic$foundations$of$development• The$interaction$of$heredity$and$environment:$The$nature-nurture$debateGenetic(Foundations• Chromosomes• Genes• DNAGenetic(Foundations• Humans$have$approx.$20,000$ genes$• Many$genes$collabor ate• The$environm ent$affects$the$activity$of$genes• Human$Genome$Project$(2012)Cell(division• Mitosis:$• Two new$cells$are$formed,$each$containing$the$same$DNA$as$the$original$cell$• Meiosis:$$• Eggs$and$sperm$(or$gametes)$are$formed• Each$has$only$½$of$the$genetic$material$of$the$parent$cell$Genetic(Foundations• Fertilization:$$• Zygote:$• Variability$of$genesGenotype(and(Phenotype• Genotype$-- all$of$a$person’s$genetic$material$• Phenotype$-- observable$characteristicsDominant(and(Recessive(Inheritance• Dominantú heterozygosity,$wi t h$a $dominant$gene• Recessiveú homozygosity,$with$$no$dominant$geneDominant-Recessive(InheritanceDominant-Recessive(TraitsDominant-Recessive(TraitsDominant-Recessive(TraitsIncomplete(Dominance(and(Polygenetic(InheritanceIncompleteDominance• Both$alleles$of$a$single$gene$are$expressedPolygenicInheritance• Many$genes$combine$to$influence$a$trait.Genetic(AbnormalitiesChromosomal5Abnormalities5• Abnormalities$caused$by$not$having$the$typical$set$of$23$chromosomes• See$figure$2.4$in$textbookGene-linked5Abnormalities• Abnormalities$caused$by$defective$g enes• See$figure$2.5$in$textbook$Beha vior(Genetics• Heritability:• Statistical$estimate$of$heritable$influence$on$trait$variance$in$a$pop ulation• Ranges$from$0$to$1.00Heritability(IndexMeasuring(Heritability• Family5Studies• The$degree$to$which$biological$relatives$share$traits• Adoption5Studies• The$degree$to$which$adopted$children$$resemble$biological$relatives$or$ad opted$family$members• Twin5Studies• Compares$the$degree$t o$which$monozygotic$and$dizygotic$twins$resemble $each$other$for$a$traitHeredity(and(the(Environment:((Working(together• Reaction$range• Potential$variation$in$a$trait• Canalization• Heritable$restrictions$on$the$range$of$trait$developmentThe Concept of Range of Reaction for Intellectual PerformanceIntellectual Performance (IQ)HighRestricted EnrichedAverageAveragechild A child B child CReaction RangeLowType of Environment?Bi-directionality(of(genes(and(en vir onmentGenotype(x(Environment((((G(x(E)(Correlations• 3$ways$the$environment$reflects$or$reinforces$genetic$diff erencesú Passive:ú Reactive5or5E vocative:ú Active5 or5Niche5Picking:The(Epigenetic(View• The$bidirectional$interchange$between$heredity$and$the$environment$causes$development(Gottlieb,$Wahlsten,$&$Lickliter,$2006 )Gene(X(Environment((((((((((((((((((G(x(E)(Interaction(• The$interaction$of$a$specific$measured$variation$in$DNA$and$a$specific$measured$ aspect$of$the$environmentGene(by(en vir onment(inter actions0123456789non-stressful environment stressful environmentDepressionGenotype by environment interactionGENE AGENE BActivity:Traits(Influenced(by(Heredity(&(En vironmentVIDEO: Environmental and genetic influences on intelligence