© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Chapter Two Heredity and the Environment

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved The Process of Genetic Transmission Genotype – a specific set of genes inherited from one’s parents –Only identical twins have identical genotype Phenotype – observable and measurable genetic expressions of individual physical and behavioral characteristics

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved The Process of Genetic Transmission Oviduct – sperm and egg unite here Zygote – a new organism Ovum – female egg, the largest cell of human body Sperm – male fertilization cell, the smallest cell in body Chromosomes and Genes – located in cell nucleus

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved The Process of Genetic Transmission Chromosomes and Genes –23 chromosomes from each parent Homologous – father’s sperm –46 chromosomes form new human being –Reproductive cells have only 23 chromosomes, undergoes cell division called meiosis –“Crossing over” creates genetic variability during meiosis –Mitosis occurs in autosomes and sex chromosomes

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved The Process of Genetic Transmission Genes, DNA, and Proteins –DNA – deoxyribonucleic acid, binding element of a chromosome Nucleotide – nitrogen base –Genes Chromosome’s DNA molecule Genes trigger production of proteins by DNA splitting and replicating

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Genetic Influences on Development Genes never work in isolation Transmission of Traits: A Basic Model –Alleles – alternative forms of a gene –Homozygous – alleles from both parents are the same for a specific gene or trait –Heterozygous – alleles from both parents are different for a specific gene or trait

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Genetic Influences on Development Transmission of Traits: A Basic Model –Codominance pattern of two alleles –Dominant allele –Recessive allele

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Fr Table 2-1 MotherFather Curly hairRecessive - Straight CCCCCCSS CS Curly hair CC S C Recessive gene for straight hair Dominant gene for curly hair

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Genetic Influences on Development Genes on the Sex Chromosomes: Exceptions to the Rule –Sex chromosomes – XX for females, XY for males –Many X-linked genes are more common in males than females –Hemophilia – X-linked recessive allele

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Genetic Influences on Development Interactions Among Genes –Of interest: IQ, creativity, sociability, genius? –Modifier genes have indirect effect on expressions of other genes Genetic Disorders –Genes can have positive and negative effects on development –Why harmful alleles survive – PKU?

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Mother (carrier) Father (carrier) Normal childPhenylketonuria Carrier NNPPNNPP PN NP

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Genetic Influences on Development Chromosome Abnormalities –Down Syndrome –Sex-Chromosome Anomalies: Turner Syndrome (XO pattern) Triple-X (XXX pattern) Klinefelter’s syndrome Fragile X syndrome

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Genetic Counseling and Genetic Engineering Genetic counseling – for parents facing birth of abnormal or special child (preventive genetic counseling?) Testing for defective genetic genes –XYY criminal predisposition? Assisted reproductive techniques

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Genetic Counseling and Genetic Engineering Prenatal Diagnostic Techniques –Commonly used tests Amniocentesis Chorionic villi sampling Genetic markers for Alzheimer’s disease (its link to Down Syndrome?), Huntington disease Alphafetoprotein assay (AFP) Ultrasound

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Genetic Counseling and Genetic Engineering Prenatal Diagnostic Techniques –Ethical and Policy Issues & new technology –Genetic Information Nondiscrimination Act of 2007 Gene Therapy –Modified viruses –Human Genome Project –Genetic engineering and genetic manipulation

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Heredity-Environment Interactions Debate in human development: –Role of heredity and maturational factors vs. Role of learning and experience –After 1926, Watson and behaviorists flourish –Contemporary psychologists see interaction of both in development – genes help shape environment and environments influence genes

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Heredity-Environment Interactions How Environment Influences the Expression of Genes –Range of reaction –Genes set boundaries on the range of their behavioral possibilities –Restricted and enriched environments –Canalization and restricted development –Mutual influence of genes and environment –Timing of environmental influence

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Achievement test score Environment EnrichedRestricted Child A Child B Child C Child B’s Range Child A’s Range Child C’s Range

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Individual Development Environment (Physical, Social, Cultural) Genetic activity Behavior Neural activity

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Heredity-Environment Interactions How Genetic Makeup Helps to Shape the Environment –Passive genetic-environmental interaction: environment encourages predispositions –Evocative genetic-environmental interaction: inherited tendencies evoke certain responses from others –Active genetic-environmental interaction: genetic makeups encourage “niche picking”

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Heredity, Environment, and Individual Differences Field of human behavior genetics arose in 1960s Behavior geneticists calculate heritability factors Misconceptions about the study of behavior genetics

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Heredity, Environment, and Individual Differences Methods of Studying Individual Differences –Adoption and Twin Studies: monozygotic and dizygotic –Shared and Nonshared Environments People are active creators in their environment (intentional, unintentional)

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Heredity, Environment, and Individual Differences Some Individual Differences and Their Contributors –Intellectual characteristics – heredity contributes to individual differences Timing and rate of development Some specific cognitive abilities –IQ scores and biological parents

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved Heredity, Environment, and Individual Differences Some Individual Differences and Their Contributors –Temperament and Personality Typical mode response to environment Difficult, easy, and slow-to-warm Cultural differences –Ethnicity and race differences –“Goodness of fit”

© 2009 The McGraw-Hill Companies, Inc. All Rights Reserved The End