1. Introductory Psychology: Biological Bases of Behavior
AP psychology: Unit II
Topic: Behavior Genetics
“We share half of our genes with a banana…” – Robert May

2. What is Behavior Genetics?
The study of the relative power & limits of genetics and environmental influences on behavior
Nature v. nurture

3. The Biological Bases: Basic Genetic Principles
Part one

4. Basics: Genes – Our Code for Life
Chromosomes
Strands of DNA (deoxyribonucleic acid) that carry genetic information; located in the nucleus of every human cell
Humans: 46 chromosomes (23/23)
Genes
Segments of DNA molecules
Contain code for production of proteins
Key functional units in hereditary transmission (biological development)
Sex Chromosomes
Autosomes

6. Basics: Genes – Our Code for Life
Like chromosomes, genes operate in pairs, with one gene in each pair coming from each parent
Homozygous Condition
Paired genes are the same
Heterozygous Condition
Paired genes are different
In this case, one gene in the pair masks the other

7. Basics: Genes – Our Code for Life
Genotype
A person’s genetic makeup; determined at conception and fixed forever
Phenotype
The ways in which a person’s genotype is manifested in observable characteristics
Person’s actual physical characteristics
Height, eye color, disease history, general disposition
Different genotypes can yield the same phenotype
May change over time

8. Basics: Genes – Our Code for Life
Genetic & Chromosomal Problems
Cystic Fibrosis
Two recessive genes;
Disorder that affects respiratory & digestive tract
Sickle Cell Anemia
Two recessive genes; blood disorder
Abnormality in shape of red blood cells
Tay-Sachs Disorder
Two recessive genes; fatal neurological disorder
Destroys nerve cells in the brain and spinal cord

9. Basics: Genes – Our Code for Life
Genetic & Chromosomal Problems
Down Syndrome
Extra chromosome (21st pair)
Causes lifelong intellectual disability, developmental delays, and health problems
Turner Syndrome
Missing X chromosome (e.g. infertility, sexually underdeveloped, etc.)

10. The Biological Bases: Heritability
Part two
Twin studies:
The ultimate nature-versus-nurture laboratory

11. What is Heritability?
The extent to which the differences among people are attributable to their genes
Studies focus on:
Individual differences v. Group differences?
Obesity: (2010)
Americans – 28%
Japanese – 3%
Nature v. Nurture?
We all have the capacity to learn language, but we do not all speak the exact same

12. Heritability: Twin Studies
Monozygotic
Dizygotic

13. Heritability: Jim Lewis & Jim Springer
Middle class
Wife: Betty
Son: James Alan (Allan)
Dog: Toy
Hobby: Woodworking
Bad Habits: Chain smoker, fingernail biting
Other: Drove a Chevy, watched stock-car racing
Health conditions: High blood pressure & occasional migraines
Identical twins
Gerald Levey and
Mark Newman

14. Idealized View of an Adoption Study
Parent-offspring resemblance can arise for both genetic and environmental reasons
Genetic and environmental contributions to parent-offspring; Resemblance are in principle separate
Bio and Rearing Parent
Birth Parent
Adoptive Parent
Genetic
Environmental
Genetic
Environmental
Offspring
Offspring

16. Heritability: Twin Studies
Used to determine the heritability of a trait

17. Heritability: Adoption Studies
Compare children's traits with those of their biological and adopted parents
Studies suggest that adoptees tend to be more similar to their biological parents
Two adopted children in the same household bear no more resemblance to each other than two biological siblings - in terms of personality

18. Heritability: Adoption Studies
S0 does parenting even have an effect?
It has an effect on biologically related and unrelated children alike
Early stimulation is key to proper development
Effects attitudes, values, manners, beliefs, faith, etc.
Different from temperament and personality…
“Heredity deals the cards, environment plays the hand…”

19. “Mutation and natural selection are the engines of evolution”
Genetic mutations
What causes a genetic mutation?
How often do mutations occur?
How have mutations been of benefit to the human population?

20. Nature vs. Nurture
and
Gender

21. Sexual Birth Defects Ambiguous genitalia
Androgen insensitivity syndrome (AIS)
Fetal tissue insensitivity to male hormones
Affects genital development
Congenital adrenal hyperplasia (CAH)
Inherited condition – affects hormone production
Excessive manufacture of male hormones
Sex chromosome disorders
Baby has mixture of XX and XY sex chromosomes
Y chromosome may be inactive; one of X chromosomes may have a tine Y segment attached
Maternal factors
Other factors during pregnancy that impact hormone production

22. Understanding Gender Gender roles Social learning theory
Our expectations about the way men and women behave
Influenced by culture
Gender identity
Sense of being male or female
Gender-typing
Exhibiting traditional gender traits and interests
Transgender
Persons whose gender identity, gender expression or behavior does not conform to sex assigned at birth
Social learning theory
Children learn gender-linked behavior by observing and imitating and being rewarded or punished
Gender schema theory
Concept of what it means to be male or female
Gender becomes lens through which we view our experiences
Based on social learning theory
How have gender roles changed over time? Why?
Identify traditional gender roles
Should transgender students be allowed to use restrooms of sex with which they identify?
In what ways are gender-linked behavior attributed to the social learning theory?