1. Biological Bases of Behavior
Unit 3
Biological Bases of Behavior

2. Module 14: Behavioral Genetics
Do First
Be Aware Of:
Answer the Fact or Falsehood? questions by indicating if they are true or false.
If FALSE, make sure that you explain WHY.
Unit 3 Test – Friday, 9/22
Rough Draft of Research Proposal Due 9/22
Module 14 for HW

3. NEW! Homework Planner!

4. Module 14 Objective
SWBAT explain how heredity (genes and heritability) and genes/environment interact, paying specific attention to twin and adoption studies, monozygotic vs. dizygotic twins, and molecular genetics

5. Genes – the Code for Life
Behavioral geneticist
Scientist who studies the impact of genes on your behavior
Compares heredity vs. the environment’s influence on human behavior

6. Genes – the Code for Life
DNA
Deoxyribonucleic acid
Stores the ‘information’ and instructions that build an organism
Genes
Sections of DNA that code for a specific function, look, or purpose
Active genes are expressed and determine aspects about the organism
Inactive genes do not
Chromosome
Thread-like division of the DNA molecule; contains genes
Genome
The entire collection of you; the whole of an organism’s genetic structure and code

7. What does this mean for behavior?
Two types of twins to study:
Identical twins (monozygotic)
Fraternal twins (dizogtic)

8. What does this mean for behavior?
Identical/monozygotic:
Developed from a single sperm fertilizing a single egg
Mono – zygotic = one zygote split to form two people
Share ALL of their genetic code
Fraternal/dizygotic:
Developed from TWO separate sperm cells fertilizing TWO egg cells – develop at same time
Di – zygotic = two zygotes form two people
Typical brothers/sisters – share about 50% of their DNA in common

9. Twin and Adoption Studies
Given the extreme importance of this subject, University of Minnesota did a long-running twin and adoption study
Twins separated at birth were found later and asked numerous questions about their lives and habits
Remarkably, IDENTICAL twins – even those separated at birth – share almost 70% of their traits, on average
Fraternal twins and siblings share about 40-50% of their traits on average
What does this say about genetic influences on behavior and personality?

10. It’s All Relative – Bio vs. Adoptive
Genetic/biological relatives – fathers, mothers, siblings, your (hypothetical) children, cousins, etc. share some genetic material in common
You are much more likely to share traits in common w/ your parents than a random person
ADOPTED children share substantially less in common with their adoptive parents
However, they still have a higher rate of similarity to their adoptive parents than random strangers
What does this say about environment’s influence on behavior?

11. The New Frontier – Molecular Genetics
Subfield of biology that studies molecular structure and function of genes
Why are black people more susceptible to heart disease? Why are white people more susceptible to Alzheimers?
Are certain people pre- programmed based on their race for different languages or conditions?
Why do some people NEVER get sick, some people are able to power through sickness, and others get sick all the time?
Heritability
The amount of variation of a trait in people we can attribute to genetics
“differences among people”
To what extent is height/weight/intelligence genetic?
Gene-environment interaction
Interplay that occurs when one factor (environment) depends on another factor (genetics)
How does being poor change the level of intellect someone gets?
One Brazilian case study indicates A LOT:
One twin was raised in wealth, was 5 inches taller, and scored higher on IQ tests
Other twin was raised in poverty, was short and underweight, and scored lower

12. Molecular Genetics Epigenetics:
Remember when we said genes and natural selection determine what you hand down?
Well, we were wrong.
Epigenetic is the study of how the environment can cause DIFFERENT genes to be expressed – ie, in times of food shortages, women will have children who grow to be shorter
Allows an organism to quickly adapt its offspring to unexpected/sudden changes in an environment
Potentially a form of evolution “in the short term” or adaptation “for the long term”