Download Biological and Environmental Foundations

Biological and Environmental
Foundations
Chapter 2
Genotypes and Phenotypes
 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
Sex
Chromosomes
Gametes
Zygote
The 22 pairs of chromosomes that are
not sex chromosomes
• 23rd pair of chromosomes
• Determines sex
• XX = female, XY = male
Sex cells: Sperm and ova
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 21st 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
Individualistic
 People define themselves as
 People define themselves as
part of a group
 Stress importance of group
goals over individual goals
 Value interdependent self
 More common in Asian
societies
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 WellBeing?
Well-Being Indicator
U.S. Rank
Childhood Poverty
25
Canadian
Rank
16
Infant Death
26
16
Teen Pregnancy
28
21
Education Spending
12
6
Health Spending
16
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