Prof. Greg Francis 6/16/081Genetic bases of developmentIIE 366: DevelopmentalPsychologyGreg FrancisLecture 05Chapter 2: Genetic Bases ofChild DevelopmentModule 2.1 Mechanisms of HeredityModule 2.2 Heredity, Environment, andDevelopmentChildren and Their Development, 4/e by Robert Kail2.1 Mechanisms of HeredityThe Biology of HereditySingle Gene InheritanceGenetic Disorders2.1 The Biology of Heredity The first 22 pairsof chromosomesare autosomes(about the samesize) The 23rd pair isthe sexchromosomes Can vary in sizeThe Biology of Heredity2.1 The Biology of Heredity Genotype is one’s completeset of genes Phenotype is one’s physical,behavioral, and psychologicalfeatures The expression of genes Environmental influencesProf. Greg Francis 6/16/0822.1 Single Gene Inheritance A gene is a group ofDNA bases thatprovide biochmeicalinstructions forproducing aminoacids, proteins, andenzyms Alleles are differentforms of genes2.1 Single Gene Inheritance Pairs of alleles can be either homozygous (same allels in the pair of chromosomes) heterozygous (different allels in the pair of chromosomes) Dominant allele: its chemical instructions are followed Recessive allele: its chemical instructions are ignored Incomplete dominance: one allele doesn’t dominate theother completelySickle Cell Trait: An Example ofIncomplete Dominance2.1: Single Gene Inheritance2.1 Genetic Disorders: Inheriteddisorders Many disorders are triggered when a childinherits two recessive alleles Examples include cystic fibrosis, PKU, albinism,and Tay-sachs disease Most inherited disorders are very rare2.1 Genetic Disorders: Inheriteddisorders Tay-sachs disease No cure Normal at birth Deterioration of the central nervous system Death by age 4 Absence of an enzyme called Hex A -> leads to build up of GM2 in the brainDisorder versus carrier Tay-sachs disease European Jews: 1 in 3000births have the disorder More people carry one of thealleles European Jews: 1 in 30 Most non-JewishCaucasians: 1 in 300 French-Canadians: 1 in 30 Irish: 1 in 41Prof. Greg Francis 6/16/0832.1 Genetic Disorders: Abnormalnumber of chromosomes Some people areborn with too many,too few, ordamagedchromosomes People with DownSyndrome usuallyhave an extra 21stchromosome2.1 Genetic Disorders: Abnormalnumber of chromosomes A number of disorders(e.g., Turner’sSyndrome,Klinefelter’sSyndrome, XYYcomplement, XXXSyndrome) are causedby missing or extra sexchromosomes2.2 Heredity, Environment, andDevelopmentBehavioral GeneticsPaths From Genes to Behavior2.2 Behavioral Genetics We need to be careful to remember that what weidentify as behavioral characteristics do netnecessarily correspond directly to geneticbehaviors Genes deal with enzymes, proteins, and amino acids2.2 Behavioral Genetics Some genes exhibitpleiotropy A single gene is oftenrelated to severaldifferent behaviors ortraits Albinos lack pigment intheir skin and have ahigh frequency ofcrossed eyes2.2 Behavioral Genetics Many behavioral genotypes reflect polygenic inheritance,which involves many genes This explains why there can be so many variations of a traitProf. Greg Francis 6/16/084An Example of Polygenic Inheritance2.2: Behavioral GeneticsAn Example of Polygenic Inheritance2.2: Behavioral Genetics2.2 Behavioral Genetics Behavioral geneticists rely upon twin studies andadoption studies Cognitive abilities, psychological disorders,substance abuse, and personality are all affectedby heredity2.2 Paths From Genes toBehavior The behavioral consequences of genetic instructions depend onthe environment in which those instructions develop Heredity and environment interact dynamically throughoutdevelopment. Genes can influence the kind of environment to which a child isexposed Environmental influences typically make children within a familydifferent.The Relation Between Genes andEnvironment2.2 Paths From Genes to BehaviorNext time Nature versus nurture Reaction range Families Social