Biological and Environmental Foundations
Genetic Foundations
 Phenotypes- observable characteristics
 Genotypes- genetic information that determines our characteristics
 Chromosomes- within the nucleus of the cell are rodlike structures that store and
transmit genetic information. Chromosomes come in 23 matching pairs (except
sex chromosomes, which are X and Y)
 DNA- chemical substances that make up chromosomes- the double helix structure
 Genes- a segment of DNA on the chromosome. We share 98% of our DNA with
chimps- so that little extra bit is responsible for our upright gait and language and
cognitive abilities.
 Karyotype is a photograph of human chromosomes.
 Mitosis is the process of duplication of the normal cells, producing exact copies.
The Sex Cells
 Gametes are the sex cell, sperm and ovum. Each contains 23 chromosomes, so
that when they combine to form a new person, the fertilized egg will have 23 pairs
of chromosomes.
 Meiosis is the process of forming gametes with 23 chromosomes.
 Zygote is produced by sperm and ovum uniting in fertilization.
 Autosomes are matching pairs of chromosomes- 22 pairs.
 Sex chromosomes are the 23rd pair, either XX for a female or XY for a male.
Multiple births relates to family history of twins, older maternal age, normal build
women and later births or use of fertility drugs.
 Fraternal/ dizygotic twins are most common twin, produced by fertilization of 2
ova by 2 sperm. These twins are no more alike than any siblings.
 Identical/ monozygotic twins occur when a fertilized zygote separates into 2
clusters of cells that become 2 individuals. 3/ 1,000 births.
Genetic inheritance
 Homozygous inheritance results when a pair of autosomes match, so the child
reflects the similar gene characteristic.
 Heterozygous inheritance occurs when the genes for a trait are not the same- so
the relationship between the 2 determines which trait will be displayed.
 Dominant-recessive inheritance determines what traits are displayed. The
dominant gene will be displayed, while the recessive trait will go underground,
held in the genetic matrix.
 Carriers have a recessive gene that can be passed to a child and be displayed in a
later generation.
o Phenyketonuria is a defect in processing proteins and is the product of
recessive genes. Because all children are tested for PKU disease and the
disease can be controlled by a low protein diet, these children can escape
brain damage and mental retardation.
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o Huntington disease (nervous system degeneration) is carried on a
dominant gene and most diseases like that are so serious that the child
doesn’t live to pass the disease on to later generations. Huntingtons,
however doesn’t display until age 35+, so many people do reproduce, not
knowing their genetic disorder til too late.
Codominance occurs when both genes influence a characteristic.
o Sickle cell trait is present in many African Americans, but Sickle cell
anemia occurs when the child inherits 2 recessive genes. Because the red
blood cells are deformed, they clog the flow of blood and the sufferer has
attacks of pain, swelling and tissue damage. Most die in the first 20 years.
Dominant and recessive characteristics: dark hair dominates blond hair;
dimples dominate over no dimples, Type A blood dominates Type O blood, Rhpositive blood dominates Rh-negative blood.
Dominant and recessive diseases
o Recessive diseases
 Cystic fibrosis
 PKU disease
 Sickle cell anemia
 Tay-Sachs disease
o Dominant diseases
 Huntington disease
 Marfan syndrome
o X-linked diseases
 Duchenne muscular dystrophy
 Hemophilia
 Diabetes insipidus
X-linked inheritance affects males more often since they don’t have a matching
X chromosome to block recessive inheritance on the X chromosome. Hemophilia
mostly occurs in boys. Other disabilities afflict boys more often: miscarriage,
infant death, birth defects, learning disabilities, mental retardation.
Genetic imprinting – genes are imprinted, chemically marked so that one
member of the pair is activated, regardless of its makeup. Diabetes is more often
passed from the father. Asthma is more often passed from mothers. Fragile X
syndrome results in moderate mental retardation, and autism yet it is expressed
only when passed from the mother.
Mutation is a sudden, permanent change in DNA. Radiation exposure results in
mutation.
Polygenic inheritance occurs when many genes determine the characteristic.
Chromosomal Abnormalities generally occur during defects in meiosis when the sex
cells are being formed. A chromosome pair won’t separate completely, etc.
 Down syndrome is the most common chromosomal disorder, 1/ 800 births.
Symptoms are mental retardation, memory, speech problems, slow motor
development. There are distinct physical features in the face, often cataracts, heart
and intestinal defects. With adequate stimulation and therapy, they can develop
more normally. Risk increases with age of mother (1/30 at age 45)
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Abnormalities of the sex chromosomes- when they are severe, most pregnancies
spontaneously abort in miscarriage.
o XYY syndrome- males with specific learning disabilities.
o XXX syndrome- girls with reading and vocabulary difficulties.
o Klinefelter syndrome (XXY) boys with physical disabilities.
o Turner syndrome (XO) girls who are infertile, without female organs,
and disabilities in spatial relationships.
Reproductive choices
 Genetic counseling can assess a couple’s chances of producing a child with a
hereditary disorder. This is essential if either person has a family history of
disease or disorder. They can detect if a parent is a carrier of a disease.
 Prenatal diagnostic methods permit detection of problems before birth, so the
parents can make a decision about carrying baby to term.
o Amniocentesis- testing a sample of fluid in the uterus to examine fetal
cells for defects. 11 – 14 weeks after conception.
o Chorionic villus sampling retrieving tissue from the membrane
surrounding the fetus to examine cells. Can be done at 6 – 8 weeks. Risks
of miscarriage and limb deformities.
o Fetoscopy - a scope with light is inserted to visually inspect the fetus for
gross abnormalities. 15 – 18 weeks. Some risk of miscarriage.
o Ultrasound- reflection of sound waves creates a picture of fetus on a
screen.
o Maternal blood analysis can be done by 2nd month of pregnancy, when
levels of alpha-fetoprotein may indicate some problems, genetic defects.
o Preimplantation genetic diagnosis- removing a cell or 2 from a zygote
that is prepared to be implanted in the mother after in vitro fertilization.
 Genetic engineering is developing in order to correct hereditary defects. Genes
have been identified by the Human Genome Project that link to severe diseases
such as cystic fibrosis, Huntington disease, Duchenne muscular dystrophy, etc.
Gene therapy occurs when healthy genes are put into the defective cells to
correct an abnormality.
o Social/ moral issues of reproductive technologies
 Donor insemination- using sperm from an anonymous donor
when the husband has problems with fertility.
 In vitro fertilization- removing the mother’s ova, fertilizing them
in a dish of nutrients and implanting the zygote. Sex sorting can be
done to ensure a girl or boy- particularly important if parents carry
an X-linked disease.
 Surrogate mothers are used when a woman can’t carry a
pregnancy herself. The surrogate carries the implanted zygote to
term and is paid a fee. Sometimes family members offer to be
surrogates.
 Cloning is only known to be successful in some animals, but there
is reason to believe some scientists are working toward cloning
humans- possibly to harvest parts. Very controversial.
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Genetic testing is suggested for people holding high risks for genetic diseases.
There are fears that general testing could result in discrimination against people
who may have genes for cancer, heart disease, etc.
Adoption has become more popular as young adults begin thinking about having
babies later and may have problems conceiving. More young women are keeping
their own babies, so the pool of healthy adoptees is shrinking. As a result many
babies are being adopted from other countries. Adopted children do have more
learning and emotional difficulties than other children, particularly if they are
adopted after infancy. In general, most adoptees develop normally and are well
adjusted as adults.
Environmental contexts
 Family is a powerful influence on development, attitudes, attachment, social skill
development. All members of the family influence all other members.
o Direct Influences- the direct effects of your behavior on others. Kindness
is usually returned with kindness, abusive attitudes return hostility.
o Indirect influences- the relationship between 2 members of the family is
affected by a third. The warmth of the marital relationship affects the
security and health of the children. Abuse of one person affects others.
Third parties can mediate the influences of more direct members- such as
a grandparent can mediate effects of disturbed parents on a child.
o Adapting to change – change is the name of the game in human
development, nothing stays the same for long. Well-adjusted people learn
to roll with the punches and find something positive.
 Socioeconomic status is stratified by:
o Years of education
o Prestige and skill required by job
o Income
o SES affects many aspects of a family’s function- health, safety, education,
size of family, values, parenting styles, verbal styles with babies,
expectations for youth.
 Poverty threatens the development of every member of a family. Poverty has
increased in the past 30 years. 12% of US and Canada are in poverty. It is hardest
on families with young children and the elderly, as well as minorities & women.
The child poverty rate is higher in the US than any other Western country.
Multiple stressors caused by poverty affect the stability of the family. There is
little energy left over for parenting children. Safety is a huge concern. Many
deteriorate into homelessness. Many homeless are suffering mental disabilities.
Most homeless are women with children under age 5.
 Neighborhoods offer socialization experiences for children. Simply living in a
healthier, safer neighborhood induces better physical & mental health & school
achievement. Poorer families benefit from neighborhood resources, parks, afterschool programs, etc. Neighborhood programs reduce stress on parents.
 Towns and Cities also affect children’s development. Small towns offer more
personal connections among members. Children have more opportunities to
develop leadership skills. Larger cities offer more museums, ball games, music
venues, academic challenges. There is more isolation in cities, though.
Cultural Context
 Cultural values in our general culture support independence of members.
However, many minority cultures emphasize family interdependence, helping one
another, supporting the elderly in the extended family structure.
o Subcultures are groups of people with beliefs and customs that differ
from the larger culture.
o Extended family households are particularly common in AfricanAmerican culture- where 3 or more generations live together. This is also
common in Asian, Native American, & Hispanic cultures.
o Collectivist societies are those where people define themselves as part of
a group and stress group goals over individual goals. (Eastern)
o Individualistic societies are those where people think of themselves as
separate entities and are very concerned about their own goals. (Western)
 Public policies are laws and government programs that should improve life for
the population. These have to do with public housing, reducing crime, increasing
welfare or minimum wages, educational policies and funding.
o For children, youth, & families policies concern child poverty, infant
mortality, teen pregnancy rates, education and health, enforcing child
support, vocational training.
o For the elderly policies concern social security benefits, age
discrimination and abuse, health benefits, safety.
Heredity and environment affect one another
 Heritability estimates measure the extent that traits are inherited genetically.
o Kinship studies compare characteristics of family members. Twins are
compared on certain traits, parents and children, parents and adoptees.
 Concordance rates are the percentage of instances when the 2nd twin shows a
trait when it is present in one twin. Range is 0 to 100%- 100% means a trait is
present 100% of the time in the 2nd twin when found in one twin. Intelligence has
.50 heritability in twins. Genetics explains half the variation in intelligence.
Personality traits show less heritability than intelligence. Schizophrenia has a 50%
concordance rate in identical twins, 18% for fraternal twins (still much higher
than in the general population) Depression is 69% in identical twins, 25% in
fraternal twins. Heritability estimates can be misapplied and used to discriminate
against groups. This was the justification for the Holocaust in Germany – to rid
the society of poor genetic specimens- except the groups deemed undesirable
extended way beyond Jews to blacks, those with mental defects, gays, etc. The
fact is that environment has a great influence on what characteristics are displayed
and how disabilities are overcome.
 Reaction range is your unique response to the environment. So your potential
can be maximized or inhibited depending on stimulation in the environment.
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Canalization is the tendency of heredity to restrict the development of a
characteristic to a few outcomes. Strongly canalized behaviors are very
genetically based and not subject to much environmental impact.
Genetic-environmental correlation – our genes influence the environments we
are exposed to.
o Passive correlation is when the child has no control over the
environment. Parents construct a certain environment into which the child
comes and adapts.
o Evocative correlation is when the child evokes responses based on
his/her own heredity. An active baby induces others to pay attention and
respond to him. An irritable baby induces impatience in caretakers.
o Active correlation is more common at older ages as children choose
activities and friends to fit their nature.
 Niche-picking is the active choice of environments that fit us. This
may be why identical twins separated at birth, when reunited find
they share many preferences.
o Environmental influences on gene expression- the process of influence
is bi-directional.
 Epigenesis means the development resulting from ongoing
bidirectional exchanges between heredity and environment. All
relationships challenge us to develop out of our comfort zone. We
learn who we are as we interact in the larger world.