Biological and Environmental Foundations

Chapter 2

Genotypes and Phenotypes

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Genotype

 Individuals’ unique genetic makeup

Phenotype

 Directly observable characteristics  Example: hair color, eye color, height, etc.

Genetic Foundations

   Chromosomes – rodlike structures inside the nucleus of each cell in the body  store and transmit genetic information Genes – segments of DNA located along the chromosomes DNA – substance of which genes and chromosomes are made.

DNA and Mitosis

   Mitosis – when DNA duplicates itself Each new cell receives an exact copy of the original chromosomes Allows one-celled fertilized ovum to develop into a complex human being composed of many cells

Chromosomes, Cells, and Sex: Terminology

Autosomes The 22 pairs of chromosomes that are not sex chromosomes Sex Chromosomes

• • •

23rd pair of chromosomes Determines sex XX = female, XY = male Gametes Sex cells: Sperm and ova Zygote Sperm and ovum united

How New People Are Formed

    New people are created when two gametes (sex cells) combine Normal # of chromosomes in a cell = 46 Gametes are formed through a cell division process called

meiosis

 Meiosis – when the number of chromosomes in each cell is halved Gametes only have 23 chromosomes  When they combine, the new zygote again has 46 chromosomes

Twins

  Fraternal/dizygotic   2 ova are released and fertilized Genetically no more alike than regular siblings Identical/monozygotic   Occurs when a zygote that has started to duplicate separates into two clusters of cells that develop into two individuals Have same genetic makeup

Alleles

   Two forms of the same gene   Remember, except for the XY pair in males, all chromosomes come in corresponding pairs Two forms of each gene occur at the same place on the chromosomes   One inherited from the mother and one from the father Each pair = Allele Homozygous – alleles from both parents are alike  Child will display the inherited trait Heterozygous – alleles from each parent differ  Relationships between the alleles determine the trait that will appear

Dominant – Recessive Inheritance

   Occurs in many heterozygous pairings Only one allele affects the child’s characteristics  Dominant allele – one that affects the child’s characteristics  Recessive – one that has no effect on the child’s characteristics Example:      allele for dark hair is dominant – D Allele for blonde hair is recessive – d DD = dark hair Dd = dark hair dd = blonde hair

X – Linked Inheritance

     When a harmful allele is carried on the X chromosome Males are more likely to be affected because their sex chromosomes do not match (XY) Females – any recessive allele on one X chromosome has a good chance of being suppressed by a dominant allele on the other X But the Y chromosome is only about 1/3 as long and lacks many corresponding genes to override those on the X Example: hemophilia

Incomplete Dominance & Polygenic Inheritance

  Incomplete Dominance    A pattern of inheritance in which both alleles are expressed Results in a combined trait intermediate between the two alleles Example:    Sickle cell trait – heterozygous One dominant and one recessive = carrier Sickle cell anemia – child inherits two recessive genes Polygenic Inheritance  Many genes influence a characteristic  Complex, still don’t know a lot about it

Genomic Imprinting and Mutation

  Genomic imprinting   Alleles are imprinted, or chemically marked, so that one pair member (either the mother’s or the father’s) is activated, regardless of its makeup Often temporary Mutation  A sudden change in a segment of DNA  Perminant

Chromosomal Abnormalities

   Most defects result from mistakes during meiosis when the ovum and sperm are formed  Chromosome pair does not separate properly  Part of a chromosome breaks off Down Syndrome  Problems with the 21 st chromosome  Failure to separate properly during meiosis, baby inherits 3 chromosomes Sex Chromosome Abnormalities  Presence of an extra chromosome (either X or Y) or absence of one X in females

Environmental Contexts for Development

      Family Socioeconomic status and family functioning Affluence Poverty Neighborhoods, towns and cities Cultural context

Family Influences on Development

    Family – social system of interdependent relationships Direct  2 – person relationships  Example: parent-child, marital partners, siblings Indirect  Third parties   Interaction between any two family members is affected by others present in the setting Example: parents who have a warm, considerate marital relationship praise and stimulate their children more Adapting to change  Changes from within and outside the family  Example: birth of a new baby, change of occupation

Socioeconomic Status (SES)

  Social status   Years of education Job prestige and skill required Economic status  Income

SES and Family Functioning

   Timing and duration of family life cycle   Lower SES – marry and have children earlier, have more children Higher SES – marry and have children later, have less children Values and expectations   Lower SES – tend to emphasize external characteristics (obedience, politeness, neatness, cleanliness) Higher SES – emphasize psychological traits (curiosity, happiness, self-direction, cognitive and social maturity) Education, status of women  Education of women fosters patterns of thinking that greatly improve quality of life for both parents and children

SES and Family Functioning (cont.)

  Communication and discipline styles   Lower SES – greater use of coercive discipline and physical punishment Higher SES – tend to use discussion techniques and teach children how to make independent decisions Children’s cognitive development  Lower SES – less likely to provide stimulation for children  Higher SES – more likely to provide simulation

Risks of Affluence

   Affluent parents – highly prestigious jobs and six-figure incomes Children:  More likely to use alcohol and other drugs  Report high levels of anxiety and depression  Report less emotional closeness and supervision from parents Unavailable parents   Overscheduled (never around) Demanding (make excessive demands for achievement)

Importance of Regularly Eating Dinner as a Family

Poverty: Who Is Poor?

 15.1% in the United States as of 2012      Parents under age 25 with young children (50 %) Elderly living alone, especially women (50%) Ethnic minorities Women Children under 18 (22%)    Hispanic children 35 % Native-American children 32 %*** (not updated) African-American children 38 %  http://www.npc.umich.edu/poverty/

Poverty: Homelessness

   On any given night, approximately 350,000 people in the U.S. have no place to live 23 % of homeless are families with children     Majority with children under age 5 Poor school attendance  Approximately 25 to 30% who are old enough do not attend school Health issues Developmental delays Homelessness mostly due to:   Decline in availability of government-supported, low-cost housing Release of mentally ill people from institutions who receive no help to adjust to ordinary life

Benefits of Strong Community Ties for Children and Adults

    Social interaction, activities – reduce family stress and enhance adjustment  Frequent contact with friends, relatives, regular religious service attendance Cooperation to provide clean, safe environment Participation in important tasks Mutual assistance

Neighborhoods

   Neighborhood resources have a greater impact on low SES young people  Impact can be either positive or negative In-school and after-school programs  Provide enrichment activities – associated with improved academic performance and reduction in emotional and behavior problems Neighborhood organizations and informal social activities  Predict increased self-confidence, school achievement, and educational aspirations

Towns and Cities

 Rural areas and small towns     Youths more likely to be given important tasks (caring for livestock, operating a snowplow, playing in the town band)  Usually alongside adults – instill strong sense of responsibility and teach practical and social skills Stronger connections between settings (ex. Schools serve as community centers, more frequent parent-teacher interaction) Active involvement in the community is likely to be greater throughout the life span Public places are relatively safe and secure

Extended Families

   Three or more generations live together More common in minority cultures Benefits  Reduces stress of poverty    More employed adults in the household Assistance for all generations    Grandparents play large roll in guiding younger generations Adults who face employment, marital, or child-rearing difficulties receive assistance and emotional support Caregiving is enhanced for children and the elderly Generally enhanced emotional bonds and support

Individualistic and Collectivistic Societies

Collectivist     People define themselves as part of a group Stress importance of group goals over individual goals Value interdependent self More common in Asian societies Individualistic     People define themselves as separate entities; separate from other people Largely concerned with individual/personal needs and goals Value independent self More common in western societies like the U.S.

Public Policies and Lifespan Development

   Public policies – laws and government programs designed to improve current conditions Example: if homelessness increases  Build more low-cost housing, raise minimum wage, increase welfare benefits Example: Obamacare

How Does the U.S. Compare to Other Nations on Indicators of Children’s Health and Well Being?

Well-Being Indicator U.S. Rank Childhood Poverty Infant Death Teen Pregnancy Education Spending Health Spending 25 26 28 12 16 Canadian Rank 16 16 21 6 4

Policies for the Elderly

    U.S. was behind the curve in policies to protect the elderly  Social Security – awarded in the U.S. in 1930s  Decade behind most Western nations 1960s – federal spending on programs for the elderly expanded  Medicare, national health insurance program Only 4% of federal budget for the elderly goes to programs other than Social Security and Medicare (which are working so well…) Most Area Agencies on Aging operate at regional and local levels   Communal and home-delivered meals, self-care education, elder abuse prevention, etc Poorly funded – help far too few people in need

How Much Does Heredity Contribute to Behavior?

  Heritability estimates    Measures extent to which individual differences in traits are due to genetic factors Ranges from 0 to 1.00

Obtained from kinship studies    Compares the characteristics of family members What percent of the time do family members/twins show a trait Ranges from 0 to 100% Example: heritability value for intelligence in children = .50

 Suggests that differences in genetic makeup explain about half of the variation in intelligence

Heredity and the Environment

 Range of reaction    Each person’s unique, genetically determined response to the environment Can apply to any characteristic 2 important points  Shows that because each person has a unique genetic makeup, we respond differently to the same environment  Sometimes different genetic – environmental combinations can make two people seem similar (when in reality they are not)

   Ben’s intelligence increases steadily with the quality of the environment Linda’s rises sharply, then falls off Ron’s begins to increase only after the environment becomes modestly stimulating

Genetic – Environmental Correlation

  Our genes influence the environments we are exposed to Changes with age   

Passive correlation

  Younger ages Child has no control over its genetic influence on environment because parents provide environments influenced by their own heredity

Evocative correlation

 Children evoke responses from the environment that are influenced by their own heredity  Responses strengthen child’s original style  Ex. Active friendly baby is likely to get more social stimulation than a passive quiet infant

Active correlation

  Children extend their experiences beyond immediate family Niche-Picking – Actively seek environments that fit with their genetic tendencies  Ex. Well-coordinated muscular child spends more time at after-school sports & musically talented child joins school band and plays violin

The Epigenetic Framework

  Views relationship between heredity and environment as

bi-directional

 Genes affect people’s behavior and experiences but their experiences and behavior also affect gene expression Epigenesis – development results from ongoing, bidirectional exchanges between heredity and all levels of the environment

    Example: providing a baby with a healthy diet increases brain growth Leads to new connections between nerve cells, which transform gene expression Opens the door to new gene-environment exchanges like advanced exploration of objects Further enhances brain growth and gene expression