Module 11: Behavior Genetics: Predicting Individual Differences

Behavior geneticists

The study of the relative power and limits of genetic and environmental influences on behavior

Heredity

The genetic transfer of characteristics from parents to offspring

Environment

Every non-genetic influence, from prenatal nutrition to the people and things around us

Chromosome

Threadlike structures made of DNA molecules that contain the genes

Where do we get our chromosomes from/how many do we get?

46 in total, 23 from mother’s egg + 23 from father’s sperm

DNA (deoxyribonucleic acid)

A complex molecule containing the genetic information that makes up the chromosomes

Genes

The biochemical units of heredity that make up the chromosomes; small segments of DNA capable of synthesizing (making) proteins

Genes are either…

Active (expressed) or inactive

Biological factors and our environment can… genes

turn on

What happens when genes are ‘turned on’?

They provide the code for creating protein molecules

Protein molecules

Body’s building blocks

Genome

The complete instructions for making an organism, consisting of all the genetic material in that organism’s chromosomes

similar

Human genomes are very… to each other

big differences in organism’s characteristics

Slight differences in DNA=

No, each offspring is very unlikely to have the exact combination of traits that they have. Each offspring is very unique

Is each offspring likely to have the exact combination of traits that they have?

No single gene predicts smarts, sexual orientation or personality. Multiple genes connect to form these traits

Which gene predicts smarts, sexual orientation, or personality

Relationship between our genetic traits and environment

Environmental influence interacts with our genetic traits

Our traits are influences by many genes, with each having a small effect

What does it mean that our traits our polygenic?

Twin and adoption studies

Twin controls heredity, while adoption controls home environment

Identical (monozygotic) twins

Individuals who developed from a single fertilized egg that split in two, creating two genetically identical organisms. Same conception + uterus, usually same birth date

they don’t always have the same number of copies of those genes repeated within their genome

Though identical twins have the same genes,

The twins may differ in their brains’ tiny wiring structures

How can one identical twin have a mental disease and one not?

Though they usually share a placenta, they sometimes have different placentas, providing one with more blood flow and nutrients than the other

Why might one identical twin have slightly better prenatal nourishment than the other?

Fraternal (dizygotic) twins

Individuals who developed from separate fertilized eggs. They are genetically no closer than ordinary siblings, but shared a prenatal environment

Genetic relatives

Biological parents and siblings

Environmental relatives

Adoptive parents and siblings

No. Shared family environment=little impact on children’s personality

Are people who grew up together (apart from identical twins) similar personality-wise?

Attitudes, values, manners, education, religion

Though their personality may not be influenced, environmental relations can sway one’s

Temperament

A person’s characteristic emotional reactivity and intensity. This is quickly apparent (obvious) and genetically influenced

It often persists throughout one’s lifetime

How long does temperament last?

Yes, they often have more similar temperaments than fraternal twins

Do identical twins have similar temperaments?

Anxiety=higher heart rate + more reactive nervous system

How does the genetic influence of anxiety lead to physiological differences?

Heritability

The proportion of variation among individuals in a group that is connected to genes

Depending on range of populations and environments

How might heritability vary?

Using twin and adoption studies

How can the heritability be mathematically estimated?

Small environment=higher heritability

Relationship between environment and heritability

Does not mean human genes have changes, but rather the environment has changed

Why might different groups (ex. adults and children) have differences in traits?

No, only individuals

Are groups different due to heritability?

Enormous adaptive capacity ad humans

ability to change as our environment changes

Adaptation

Biological mechanism that allows us to change

Our genes and environment depend on each other in order to change over time

How do our genes and experience interact with each other?

Molecular Genetics

The subfield of biology that studies the molecular structure and function of genes

Molecular Behavior Genetics

The study of how the structure and function of genes interact with our environment to influence our behavior

Examples of Complex Traits

Body weight, sexual orientation, impulsivity

Complex Traits

Our environment and many genes work together to determine these traits

Genome Association Studies (GWAS)

Study of the entire genome of a large group of people to find genetic variations associated with a phenotype

Phenotype

An observed trait or behavior

Epigenetics

The study of the molecular mechanisms by which environments can influence genetic expression (without DNA change)

Environments can trigger or block genetic expression

How do genes become active or inactive?

regulating

Genes are self-

Epigenetic Marks

Molecules that trigger or block genetic expression; they tell genes what, where, and when to do stuff

The gene there may become inactive

What happens when an epigenetic mark molecule attaches to a DNA segment?

DNA is permanent, while epigenetics are not

Which is permanent, DNA or epigenetics?