Chapter 2 Genetic and Environmental Foundations

Genotype and Phenotype An individual’s genetic information Phenotype An individual’s directly observable characteristics © szefei/Fotolia

Segment of DNA along the length of the chromosome Genetic Foundations Chromosomes Rodlike structures within the cells that store and transmit genetic information DNA Deoxyribonucleic acid, the chemical substance that makes up chromosomes Gene Segment of DNA along the length of the chromosome

Mitosis and Meiosis Mitosis Process by which DNA duplicates itself Produces new body cells containing the same genetic information Meiosis Process by which gametes (sex cells) are formed Halves the number of chromosomes normally present Leads to genetic variability

Autosomes, Sex Chromosomes, and Sex Cells 22 matching pairs of chromosomes Sex chromosomes 23rd pair of chromosomes (XX = female, XY = male) Gametes Sex cells: sperm and ovum Zygote Formed when sperm and ovum unite

Twins Fraternal/Dizygotic Result from release and fertilization of two ova Identical/Monozygotic Result when a single zygote separates to form two individuals © Blend Images/Shutterstock

Alleles Two forms of the same gene, one inherited from each parent homozygous (both alleles are alike) heterozygous (alleles differ) Occur at the same place on both chromosomes in a pair

Dominant–Recessive Inheritance Only the dominant allele affects children’s phenotypic characteristics Carriers: heterozygous (have one recessive allele) can pass recessive trait to their children Many serious diseases are product of recessive alleles

Incomplete Dominance Both alleles are expressed in the phenotype Possible results: combined trait trait that is intermediate between the two Example: sickle cell anemia

X-Linked Inheritance Figure 2.4 X-linked inheritance Figure 2.4

Genomic Imprinting, Mutation, and Polygenic Inheritance chemical marker activates one allele in a pair often temporary; may not occur in all individuals Mutation: sudden, permanent change in a segment of DNA may affect one or two genes, or many Polygenic inheritance: characteristics influenced by many genes

Chromosomal Abnormalities Down syndrome: caused by problems with 21st chromosome Sex chromosome abnormalities: caused by problems with X or Y chromosome often not recognized until adolescence © Denis Kuvaev/Shutterstock

Reproductive Choices Genetic counseling Prenatal diagnosis and fetal medicine Reproductive technologies Adoption © Monkey Business Images/Shutterstock

Reproductive Technologies Donor insemination In vitro fertilization Surrogate motherhood New technologies © Burlingham/Shutterstock

Genetic Counseling Helps couples Recommended when assess chances of hereditary disorders choose best course of action in view of risks and family goals Recommended when couple has had difficulties bearing children known genetic problems exist woman is over 35

Prenatal Diagnostic Methods Amniocentesis Chorionic villus sampling Fetoscopy Ultrasound Maternal blood analysis Ultrafast magnetic resonance imaging Preimplantation genetic diagnosis © PhotographyByMK/Shutterstock

Adoption Trends: international adoption adoption of older children adoption of children with known developmental problems Children typically exhibit some difficulties, but most fare well © Vitalinka/Shutterstock

Environmental Contexts for Development Family Socioeconomic status and family functioning Neighborhoods, towns, and cities Cultural context © Mat Hayward/Fotolia

Family Influences on Development Direct influences Indirect influences: effects of third parties Adaptation to changes within and outside the family © auremar/Fotolia

Socioeconomic Status (SES) Social status: years of education prestige of one’s job and skill it requires Economic status: income © Yanming Zhang/Shutterstock

Socioeconomic Status and Family Functioning SES is linked to: timing of marriage and parenthood family size values and expectations for children parents’ education and economic security communication and discipline styles investment in children’s cognitive development

Poverty Who Is Poor? 46 million Americans (15%) are poor Those hit hardest are: parents under age 25 with young children, especially single mothers older adults who live alone, especially women children, especially African- American, Native-American, and Hispanic children © gcelebi/Shutterstock

Homelessness Most homeless families are women with children under age 5 Many homeless children suffer from: developmental delays chronic emotional stress 25% to 30% of school-age homeless children do not attend school

What Are the Risks of Affluence? Alcohol and drug use High levels of anxiety and depression Unavailable parents: lack of emotional closeness and supervision excessive demands for achievement © Beata Wawrzyniuk/Shutterstock

Importance of Regularly Eating Dinner as a Family Figure 2.6 Relationship of regularly eating dinner with parents to affluent youths’ adjustment problems Figure 2.6 (Adapted from Luthar & Latendresse, 2005.)

Benefits of Strong Community Ties Beyond the Family Benefits of Strong Community Ties Neighborhoods: resources and social ties that promote development Towns and cities: mold children’s and adults’ daily lives Small towns: promote connection and participation © Petrenko Andriy/Shutterstock

Cultural Context Cultural values and practices: shape daily life within and outside the family Subcultures: cooperative family structures help protect members from harmful effects of poverty collectivism vs. individualism Public policies: laws and programs designed to improve current conditions

Extended Families Three or more generations living together More common in many minority cultures Benefits: reduce stress of poverty provide assistance for all generations create strong family bonds transmit culture to next generation © Hasloo Group Production Studio/Shutterstock

Individualistic and Collectivist Societies People define themselves as separate entities Independent self Collectivist People define themselves as part of a group Interdependent self

Indicators of Children’s Health and Well-Being Table 2.5 How Does the United States Compare to Other Nations on Indicators of Children’s Health and Well-Being? Table 2.5 (Sources: Canada Campaign 2000, 2009; OECD 2010; U.S. Census Bureau, 2012; U.S. Department of Education, 2012.)

Percentage of Older Adults Living in Poverty Figure 2.7 Percentage of older adults living in poverty in 20 industrialized nations Figure 2.7 (Adapted from Luxembourg Income Study, 2011.)

How Much Does Heredity Contribute to Behavior? Heritability Estimates Behavioral Genetics How Much Does Heredity Contribute to Behavior? Heritability Estimates Obtained from kinship studies Provide an estimate of proportion of individual differences in a trait attributable to heredity Range from 0 to 1.00

Gene–Environment Interaction Individuals respond differently to same environment because of genetic makeup Similar responses can result from different gene–environment combinations Figure 2.8 Gene–environment interaction, illustrated for intelligence by three children who differ in responsiveness to quality of the environment © atikinka/Shutterstock

Canalization Tendency of heredity to restrict development of some characteristics to just one or a few outcomes Ensures development of species-typical skills under many rearing conditions © photomak/Shutterstock

Gene–Environment Correlation Passive correlation Evocative correlation Active correlation: niche-picking © szefei/Shutterstock

Epigenesis Development results from bidirectional exchanges between heredity and all levels of environment Genes affect behavior and experiences Experiences and behavior affect gene expression

The Epigenetic Framework Figure 2.10 The epigenetic framework Figure 2.10 (Adapted from Gottlieb, 2007.)

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