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Infants, Children, and
Adolescents
Chapter 2
Genetic and
Environmental
Foundations
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Genetic Foundations
Chromosomes – store and
transmit genetic information
Genes – segments of DNA
located along the
chromosomes
DNA – substance of which
genes and chromosomes
are made
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DNA’s Ladderlike Structure
Figure 2.2
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Meiosis
Figure 2.3
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Meiosis Video
Crossing over process
shuffles the deck
Consequences for offspring
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Twins
Fraternal/Dizygotic –
two zygotes, or
fertilized ova
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Identical/Monozygotic
– one zygote that
divides into two
individuals
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Maternal Factors Related to
Fraternal Twinning
FACTOR
DESCRIPTION
Ethnicity
Occurs in 4 per 1,000 births among Asians, 8 per 1,000 births
among whites, 12 to 16 per 1,000 births among blacks
Family History of Twinning
Occurs more often among women whose mothers and sisters
gave birth to fraternal twins
Age
Rises with maternal age, peaking between 35 and 39 years, and
then rapidly falls
Nutrition
Occurs less often among women with poor diets; occurs more
often among women who are tall and overweight or of normal
weight as opposed to slight body build
Number of Births
Is more likely with each additional birth
Fertility drugs/
In vitro fertilization
Is more likely with fertility hormones and in vitro fertilization,
which also increase the chances of bearing triplets, quadruplets,
or quintuplets
Table 2.1
Sources: Hall, 2003; Hoekstra et al., 2008; Lashley, 2007.
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Twins` Behaviour
Are dizygotic twins essentially same
aged siblings or is there a special
relationship? What else did they
share?
What are the possibilities with
behaviour and personality
development in monozygotic twins
relative to each other?
Examples of
Dominant
and
Recessive
Characteristics
Table 2.2
Source: McKusick, 2007.
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Dominant–Recessive Inheritance
Figure 2.4
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X-Linked Inheritance
Figure 2.5
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Nature’s Adjustment
to X-Linked Inheritance
 About 106 boys are born for every 100
girls, worldwide.
 In recent decades, the proportion of male
births has declined in many industrialized
countries, which many researchers
attribute to a rise in stressful living
conditions.
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Something to think about
Why are there no fatal dominant
disorders of childhood?
Why do we still have Huntington`s
disease, a fatal dominant disorder, in
human populations?
Review / Questions?
• Math and research methods
• Correlations, case studies an experiments
• Ethics of working with children
• Human genetics 101: Missed incomplete
dominance concept – both genes can have
an effect
• Importance of cross over and shuffling the
genetic deck
• Twins and the issue with boys
Thought of the Day
Environmental toxins, genetic
mutations, and the inclusive
classroom
Genomic Imprinting
and Mutation
Imprinting
Mutation
 Chemical marker
that activates either
father’s or mother’s
gene
 Sudden,
permanent change
in a DNA segment
 Often temporary to
one generation
 Random or due to
toxins
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Mutation
Somatic Mutation:
 Normal body cells mutate, an event that can
happen at any time in life.

The DNA defect can eventually become
widespread enough to cause disease or
disability, e.g. cancer
Germline Mutation:
 Takes place in the cells that give rise to gametes.

Defective DNA is passed on to the next
generation.
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Chromosomal Abnormalities
Down syndrome
 Results from problems
with the 21st chromosome
 Video
 Why is an extra
chromosome such a
problem?
Sex chromosome
abnormalities
 Problems with the X or Y
chromosomes
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Risk of Down Syndrome and All
Chromosomal Abnormalities
by Maternal Age
Figure 2.6
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Sex Chromosomal Disorders
Table 2.4
Sources: Geerts, Steyaert, & Fryns, 2003; Kesler, 2007; Saitta & Zackai, 2005; Simpson et al., 2003.
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Reproductive Choices
Genetic counseling helps couples
assess risks and family goals related
to hereditary disorders.
Options:
Conception knowing risks
 Reproductive technologies
 Adoption

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Prenatal Diagnostic Methods
 Amniocentesis
 Chorionic villus sampling
 Fetoscopy
 Ultrasound
 Maternal blood analysis
 Preimplantation genetic
diagnosis
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Fetal Medicine
 Drugs delivered into uterus
 Surgery
 Bone marrow transplants
 Genetic engineering
 Gene therapy
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Genetic Engineering
Human Genome Project




Researchers have mapped the sequence of all human
DNA base pairs
Working on identifying all genes and their functions, in
order to understand human disorders
Thousands of genes already identified, including those
involved in cystic fibrosis, Duchenne muscular dystrophy,
Huntington disease, and many forms of cancer
Have found that a lot of our genetic material is nonfunctional
New treatments under development include gene
therapy and proteomics.
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The Alternative of Adoption
 Adopted children tend to have more
learning and emotional difficulties than
other children – Why?
 The child’s age at adoption correlates to
learning and emotional difficulties
experienced
 Most adopted children eventually fare
well
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Reproductive Technologies
 Donor insemination and in vitro
fertilization
 Surrogate motherhood (illegal in
Canada)
 New frontiers in reproductive
technology
 Ethical concerns
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Environmental Contexts
for Development
Family
Socioeconomic status
Neighborhoods
Towns and cities
Cultural context
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Family Influences on Development
Direct

Two-person relationships;
‘Bidirectional’
Indirect

Third parties; affect of marriage
health on the kids
Adapting to Change

Changes from within and
outside the family; changes as
the children grow up; society
changes (eg more single
parents)
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Socioeconomic Status and
Family Functioning
 SES : 1) years of education, 2) job and skills,
3) income/net worth
SES affects timing of family life cycle
Values and expectations
Father’s involvement
 Communication and discipline styles
 Children’s cognitive development
Remember these are tendencies not absolutes
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Quick Review
Genetic mutations and the inclusive
classroom
Reproductive medicine
Adoption
Environmental Influences : Family
Copyright © Allyn & Bacon 2011
Worldwide Education of Girls
 73 million children in the world, mostly poverty-stricken girls,
receive no education at all
 Providing education benefits to girls by providing them with
enhanced verbal skills and the empowerment to improve their
life
 Also improves:
 Family health
 Family relationships and parenting
 According to the United Nations, educating girls is the most
effective means of combating poverty, maternal and child
mortality, and disease
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Thought of the Day
Can people like Oprah really
change the world through
education reform?
Oprah video
Copyright © Allyn & Bacon 2011
Affluence
 Many affluent parents are not physically and emotionally
available for their children
 These parents often make excessive demands for
achievement
 Adolescents whose parents value achievement over
character often have academic and emotional problems
 Eight weeks of summer camp: Not by choice
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Eating Dinner Together Can
Make a Difference
Figure 2.8
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What about poverty??
What are the different
domains of development that
can be affected??
Copyright © Allyn & Bacon 2011
Neighborhoods and Schools
Neighborhoods offer resources and social ties that play
an important part in children’s development.

Higher-SES families are less dependent on their
immediate surroundings than are low-SES families.

Social ties linking families together break down in areas
with unemployment, crime, and population turnover:
i.e. stress instead of support
Children spend an average of 14,000 hours in school
by high school graduation.

Parent–school contact supports development at all ages
OR Does it?????? What is going on more and more in
Canada these days????
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The Cultural Context
 Culture shapes every aspect of
daily life.
 Different cultures have different
values; North American culture
values the independence, selfreliance, and privacy of the
family Video
 Subcultures
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 Extended-family households
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Individualist and
Collectivist Societies
Individualist
Collectivist
 People
 People
think of
themselves as
separate from
others
 Concerned with
personal goals
define
themselves as part
of a group
 Concerned with
group goals over
individual goals
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Public Policy Shortcomings
 Children without health
insurance
 Substandard child care
 Poor vocational preparation
 High-school dropouts
 US example: spend roughly
the same on education as
many other countries but . . .
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How Does the United States Fare
on Measures of Children’s Health and
Well-Being?
INDICATOR
U.S. Rank
Childhood poverty (among 25 industrialized nations considered)
25th
Infant deaths in first year (worldwide)
28th
Teenage pregnancy rate (among 28 industrialized nations
considered)
28th
Public expenditure on education as a percentage of gross domestic
product (among 22 industrialized nations considered)
12th
Public expenditure on early childhood education and child care as a
percentage of gross domestic product (among 14 industrialized
nations considered)
9th
Public expenditure on health as a percentage of total health
expenditure, public plus private (among 29 industrialized nations
considered)
Table 2.6
Sources: Canada Campaign 2000, 2009; OECD, 2006, 2008a, 2008b; UNICEF,
2007; U.S. Census Bureau, 2010; U.S. Department of Education, 2009.
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29th
Children’s Rights
1989 Convention on the
Rights of the Child (UN
General Assembly);
health, standard of living,
education, family, no
abuse or neglect etc
Influential interest groups
Children’s Defense Fund
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How Much Does Heredity
Contribute to Behavior?
Heritability
Estimates
 Portion of individual
differences attributable
to genetics
 Ranges from 0 to 1.00
Concordance
 What percent of the
time do twins both
show a trait?
 Ranges from 0 to
100%
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Reaction Range
Figure 2.9 Related to Temperament
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Genetic–Environment Correlation;
Activity level as an example
Passive correlation; from
parents
Evocative correlation; reactive
to child
Active correlation; from child

Niche-picking; watch
maker example
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Similarity in Mothers’ Interactions
for Pairs of Siblings Differing in
Genetic Relatedness
Figure 2.10
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Environmental Influences on Gene Expression
Genetic–environmental correlation is viewed as driven
by genetics
 Many researchers take issue with supremacy of
heredity.
 Bidirectional influences
 Non-debate in my opinion . . .
Parents and other caring adults can uncouple
unfavorable genetic–environmental correlations
For example, twins who displayed aggressive behavior
could be positively affected by mothers who practiced
good, positive parenting
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The Epigenetic Framework
Smoking and ADHD
example from text
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Next: Chapter 3
Prenatal Development