Transcript Separated Twins

Name human traits that you believe
to be universal.
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Communicate verbally and nonverbally
Enforce rules of etiquette
Show favoritism for in-group members (kin vs. non-kin)
Avoid incest, fear, snakes
Exchange gifts
Modesty in sexual behavior and bodily functions even if they don’t wear
clothes
Labor divided by gender
Men are more aggressive than women
Women provide more child care
All cultures have tools and tools to make tools
Beliefs about death and disease
Plan for the future
Taboos, and taboo utterances
Sanctions for crimes against society
Mechanisms for dealing with theft, murder, rape
Recognize marriage as the definition of socially recognized sexual access
to a fertile woman
Mimic, flirt, envy, empathize, joke, tease, dance, music
Myths, folklore, worldviews, poetry, attempts to control the weather
Was it Nature or Nurture?
• Not vs… rather, nature via nurture
• Over 70% of who we are is due to
genetics
– Active (expressed) vs. inactive
• What “turns on” genes to create protein
molecules?
What separates
us human to
chimp or
human to
human?
Behavior Genetics: Predicting
Individual Differences
Behavior Geneticists
study differences
weigh relative effects of heredity/environment.
Genes: Our Codes for Life
Chromosomes containing DNA (deoxyribonucleic
acid) are situated in the nucleus of a cell.
Genes: Our Codes for Life
Segments within DNA consist of genes that
make proteins to determine our development.
How/why do blue
eyes happen?
• Blue eyes are recessive
• Every person with blue eyes is related to one another
• Common ancestry based in eastern Europe (6-10,000
years ago)
– 99% of Estonians have blue eyes, 75% of Germans, 89% of
Danes
– Genetic mutation affecting OCA2 gene
• Gene codes for protein P that deals with production of melanin
• Conclusion?
– Blue eyes are not actually blue, they are a lack of brown
– What is it called when the OCA2 gene has been completely
turned off?
Genome
Genome is the set of complete instructions for
making an organism
containing all the genes in that organism.
 Thus, the human genome makes us human
Genetic predispositions
• Genetically influenced traits
– Help explain our shared human nature and
human diversity
Behavior Genetics and
Evolutionary Psychology
• Transmission of hereditary
characteristics is achieved by
biological processes
– Chromosomes carry information stored in
genes to new cells during reproduction
– Cells of ovaries and testes produce eggs and
sperm which normally have 23 chromosomes
• Of the 23 pairs of chromosomes, 22 are nonsex chromosomes
• XX (female) XY (male)
CONGRATULATIONS!!
• At fertilization, the chromosome from
the egg and sperm recombine to form a
zygote (fertilized egg)
– with 46 chromosomes that will develop into a
new individual… aka you
• So yes… congratulations, at one point in
your life, you can count yourself as a
winner
Dominant vs. Recessive Genes
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A man with red hair (recessive) marries a
woman with black hair (dominant) whose
mother had red hair. What are the chances
that their first child will have red hair? (Two
chances in four.) Black hair? (Two chances in
four.)
A man and a woman both have brown eyes,
but their first child has blue eyes. What are the
chances that their second child will have blue
eyes? (One chance in four—the odds of blue
eyes is the same regardless of how many
previous children already have blue eyes.)
The sex (not gender) of the new
individual is determined by the
sperm that fertilizes the egg
• Sperm carries X = female
• Sperm carries Y = male
– Hermaphroditism is a condition that comes
from autosomal inheritance of genes
• Autosomes are the 22 other non-sex
chromosomes
Chromosomes, Genes, and DNA
• Genes carried by chromosomes are the units
of inheritance that are sequences of DNA
• The sequence of bases along a strand
constitutes the genetic code
– The genetic code gives instructions to perform a
specific function in the body (i.e. release this protein
or that hormone)
• How can you link this to neural transfers, fight or
flight, or outward behaviors?
Transmission of incorrect number
of chromosomes
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Results in nondisjunctional errors
– Occurs when chromosomes don’t
separate correctly during cell division
– Most nondisjunctional fertilizations result
in spontaneous abortion (miscarriages)
Chromosomal Abnormalities
1. Eggs can be produced with 21 or 23
autosomes plus X chromosome
2. Eggs can be produced with 22 autosomes
without an X or with two X chromosomes
3. Sperms can be produced with 21 or 23
autosomes plus an X or a Y chromosome
4. Sperms can be produced with 22 autosomes
without a sex chromosome or with two X, two
Y, or both X and Y chromosomes
Autosomal Nondisjunction:
Trisomy-21
• Presence of 3 copies of autosome 21,
results in expression of Down syndrome
• Typically mentally retarded with a mean IQ of 50 at
age 5 and a mean life expectancy of 23 years
– Individuals tend to have round head, flat nasal
bridge, protruding tongue, small round ears,
spots in the iris of the eye, epicanthic fold in
the eyelid, poor muscle tone and coordination
Sex chromosome nondisjunctional
conditions
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More common than autosomal ones like
Trisomy 21
1. XXX condition
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Not a true syndrome, insignificant
percentage express one or more clinical
behavioral problems (irregularity in
menstruation, retardation, sterility, disturbed
personalities)
Sex chromosome nondisjunctional
conditions cont’d
2. XYY condition
• Males typically over 6 feet tall
• Acne beyond adolescence
– Prison studies in 1960’s show
aggressive/violent behavioral disorders, but
they’re not substantiated
Sex chromosome nondisjunctional
conditions cont’d
3. Turner syndrome
• Females have only one X sex
chromosome (known as XO)
• Usually normal intelligence, but evidence
of specific cognitive deficits in math,
spatial organization and visual form
perception
– Where in the brain does Turner syndrome
impact?
Turner Syndrome Females
• Typically short
• Webbed neck
• Lack ovaries and fail to develop secondary
sex characteristics
Sex chromosome nondisjunctional
conditions cont’d
4. Klinefelter syndrome
• Males arise from XXY zygote
– Small penis (they’ll have this since birth, but won’t be
evident until onset of puberty)
– Secondary sex characteristics will fail to occur
(development of chest hair, deepening of voice,
further development of testes and penis)
– Breast tissue develops
– Fat distribution of females becomes evident
– sterility
REMEMBER
•Pairs of chromosomes
each have a gene for
the same trait at the
same point on each
of the chromosomes
What happens when recessive
genes create abnormal conditions?
1. Tay-Sachs disease
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Defective gene on chromosome 15
When both parents carry the gene, child has
25% chance of developing the disease
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1 in 27 Ashkenazi Jewish population carry the
Tay-Sachs gene
Progressive loss of nerve function, obvious
at 6 months (baby fails to sit up, becomes
blind, seizures, paralyzed and dies by age 5)
2. Albinism
• Failure to synthesize or store melanin
• Abnormal nerve pathways to the brain
– Twitching of the eyes, inability to perceive
depth or 3D with both eyes
3. Phenylketonuria (PKU)
• Severe brain damage and mental retardation
UNLESS the baby is fed special diet low in
phenlylanine beginning in infancy and
continuing into adulthood
• MR happens because s/he can’t metabolize
phenylalinine and amino acid builds up in brain,
impairing brain functioning
• Hospitals do routine tests on newborns for this
disorder
4. Huntington’s disease
• Degeneration of nervous system
• Forgetfulness, tremors, jerky motions, loss
of ability to talk, temper tantrums,
blindness, death
• Onset after 30
• Lab tests can identify the gene itself, but
not its marker…
Alzheimer’s disease
• A form of Alzheimer’s has been
attributed to chromosome 21, but not all
cases are associated
Twin Studies
• Refer to articles from first day
of school
– Dizygotic, monozygotic twins
• Identical twins
– Have the same genes, just not
the same number of copy of
those genes
– 1 in 3 have separate placentas,
thus separate nourishment in
utero
• Be familiar with European
twin studies and results
Twin Studies
Studying the effects of heredity and
environment on two sets of twins - identical and
fraternal
Separated Twins
Separated Twins
Personality, Intelligence
Abilities, Attitudes
Interests, Fears
Brain Waves, Heart Rate
Separated Twins
Critics of separated twin studies note that such
similarities can be found between strangers.
Researchers point out that differences between
fraternal twins are greater than identical twins.
Conclusions?
Bob Sacha
Epigenetics
• http://www.pbs.org/wgbh/nova/body/epigenetics.
html
• How do identical twins differ if they are human
clones? How is this possible?
• What is epigenetic therapy?
• Why is it that identical twins may start to differ
during specific periods of life like puberty or
pregnancies?
Genetic Relatives vs. Environmental Relatives
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Adoption studies
Ethics
Siblings
Personality vs. attitude
Can your adopted family help you create
who you are, or are you doomed to your
genetics?
Biological Versus
Adoptive Relatives
Adoption studies, as opposed to twin studies,
suggest that adoptees (who may be biologically
unrelated) tend to be different from their
adoptive parents and siblings.
Adoptive Studies
Adoptive studies strongly point to the simple
fact that biologically related children turn out
to be different in a family. So investigators ask:
Do siblings have differing experiences?
Do siblings, despite sharing half of their genes, have
different combinations of the other half of their genes?
Ultimate question: Does parenting have an effect?
Parenting
Parenting does have an effect on biologically
related and unrelated children.
Parenting Influences
Children’s
Attitudes, Values
Manners, Beliefs
Faith, Politics
What if I told you…
• We could find a way to live without cancer?
• We could find a way to live without war or
conflict?
• We could find a way for you to have all the
pleasures and benefits of sex without the
possibility of getting pregnant?
• We could find a way to coexist with one another
in a peaceful utopia?
• What would you say to that?
Eugenics
• Scientific improving of the human genetic
code
– super races
– Should we study eugenics, at all?
• Benefits? Malevolence?
• Molecular geneticists study the
molecular structure and function of
genes.
– seek to identify specific genes influencing
behavior
– Potentially, to prevent problems before they
happen.
– risks of labeling people/discrimination.
– Prenatal screening poses hopeful
possibilities but also difficult problems as
parents become able to select their children’s
traits.
• In China and India, where boys are highly valued,
testing for an offspring’s sex has enabled selective
abortions. Millions of parents will select for health
and perhaps for brains and