Download Chapter 2 Evolution, Genetics, and Experience

Chapter 1
Evolution, Genetics, and
Experience
Men commit more violent crimes than women.
Why is this?
How many of you have ever heard the question:
Is it nature, or is it nurture?
Is it inherited, or is it learned?
Why are those questions flawed?
Thinking About the Biology of Behavior
Nature-Nurture Debate
Nature
• Influence of individual's innate qualities
*Genetics
Nurture
• Influence of learning and experience on behavior
*Gestation
*Stress levels
*Sensory stimulation
*Nutrition
*Parents
*Friends
*Culture
Thinking About the Biology of Behavior
Don’ts:
• Don’t think in
dichotomies of either
nature or nurture
• Don’t think in terms of
proportions of
nature/nurture
Do’s:
• Embrace an Interactive
Model
• Nature/nurture and
physiology/psychology are
always interacting!
Thinking About the Biology of Behavior
What question should we use to replace “Is
it nature or nurture?”
Evolution
Why do we discuss evolution in a biopsychology class?
Evolution
1. Similar brain structures
2. Nervous systems
functions similarly
*Neurons in worms work
much like ours
3. We inherited behavioral
traits from our ancestors
A Metaphor
Why do you get “goose bumps” when you are
frightened?
“When people are frightened they tend to get “goose
bumps” – erections of the hairs, especially on their arms
and shoulders. Goose bumps are useless to humans
because our shoulder and arm hairs are so short. In most
other mammals, however, hair erection makes a
frightened animal look larger and more intimidating. An
evolutionary explanation of human goose bumps is that
the behavior evolved in our remote ancestors and we
inherited the mechanisms.” –Kalat, p.4
How is genetic material passed on?
How does that contribute to genetic
diversity?
Fundamental Genetics
Mendelian Genetics
Gregor Mendel
Dichotomous Traits
• Studied inheritance in pea
• Occur in one form or the
plants
other, never in combination
True Breeding Lines
• Interbred members always
produce offspring with the
same trait
Do you inherit your traits from
you parents?
Fundamental Genetics
Mendelian Genetics
Dominant Trait
First Generation
• The trait of a
• All plants had 1B gene and
dichotomous pair that is
1w gene
expressed in a phenotype
• All plants had brown seeds
Recessive Trait
Second Generation
• Trait of a dichotomous
• ¾ plants had brown seeds
pair not expressed in the
phenotype
Fundamental Genetics
Mendelian Genetics
Phenotype
• An organisms observable
traits
Genotype
• Traits that can be passed
on through genetic
material
Chromosomes
Reproduction, Linkage, and Recombination
DNA
• Each chromosome is a
double-stranded molecule
of DNA
• Located in nucleus and
mitochondria of cells
• Each strand is a sequence
of nucleotide bases
A, T, G, C
A-T
C-G
Fundamental Genetics
Mendelian Genetics
Gene
• A sub section of a
chromosome that controls a
characteristic
Fundamental Genetics
Mendelian Genetics
Alleles
Alleles
• Two genes that control
• Located at the same locus
the same trait
of a pair of chromosomes
Fundamental Genetics
Mendelian Genetics
Homozygous
• Organisms that posses
two identical genes for a
trait
Heterozygous
• Two dif. genes for a trait
How is genetic diversity achieved?
How are natural selection and genetics
related?
Chromosomes
Reproduction, Linkage, and Recombination
Chromosomes
• Threadlike structures in
the cell nucleus that
contain the genes
• Each chromosome is a
DNA molecule
Chromosomes
Reproduction, Linkage, and Recombination
Gametes
• Egg cell, sperm cell
• Has ½ the number of
chromosomes
*23
*All other cells have
23 pairs
Chromosomes
Reproduction, Linkage, and Recombination
Meiosis
• Process of cell
division that produces
four gametes
• Accounts for much of
the genetic diversity
• For each pair you can
get one from mom or
one from dad
• 23 to the 23rd =
8,388,608
Chromosomes
Reproduction, Linkage, and Recombination
Linkage
• The tendency for traits
that are encoded on the
same chromosome to be
inherited with each other
Chromosomes
Reproduction, Linkage, and Recombination
Crossing Over
• During meiosis the
chromosomes replicate, line
up, then cross over and
split off
• Occurs at a random point
• Increases diversity –
shuffles the “genetic deck”
Chromosomes
Reproduction, Linkage, and Recombination
Mutations
• Accidental alterations in
individual genes
• Rare, but can lead to rapid
evolution
How do the genes and environment interact to
influence characteristics and behavior?
Genetic Expression
Main Ideas
• Multiple genes interact to produce complex characteristics
• Genes indirectly influence characteristics
• The environment plays a critical role in gene expression
Gene Expression
Gene Expression
• There are no genetic
effects without the
expression of a gene
• Gene “expression states”
are heritable
“Environments cannot influence gene sequences
but they can and do influence gene expression.”
- Rutter, Moffitt, and Caspi (2006)
Gene Expression
Development of Birdsong
• In songbirds, areas of the brain that are
responsible for producing song are much larger in
males than females (because of testosterone)
• Male birds that sing are born with genetics to
acquire the song of their species.
Gene Expression
Development of Birdsong
• Typically, when male birds are born they hear the
song sung by older adults – even though they cannot
sing at this point
• If they do not hear the song of their species during
the critical developmental period after birth they
typically do not acquire the song
* If they acquire a song it is usually abnormal
Gene Expression
Structural Genes
• Genes that contain info necessary for the synthesis of
types of proteins
• All cells in the body contain exact same structural genes
• The processes of building proteins from DNA can be
influenced by the environment
Gene Expression
Operator Genes
• Control structural genes
• Like switches – regulate
which genes will make
proteins an at what rate
• Determines what type of
cell it will be (blood cell,
brain cell, liver cell, etc.)
Video: Lecture 2_NOVA_Can
We Live Forever? 19:30-30:00
Gene Expression
Epigenetics
“A key feature of gene expression is that it can be altered
in a reversible way by extra-cellular signals and by
environmental influences. Although DNA starts off the
causal chain, what really matters is the expression of the
genes (in terms of messenger RNA). There are no genetic
effects without this expression. Unlike the operation of
DNA, which is active in all cells, gene expression tends to
be specific to particular body tissues and to particular
phases of development. This class of mechanisms has
been called epigenesis.”
- Rutter, Moffitt, and Caspi (2006)
Gene Expression
Epigenetics
Epigenetics
Epigenetics
• Environment influences
• Plays a major role in gene
molecules (proteins) that
expression
bind to the DNA (on top of
it)
• Accumulate throughout
life
• DNA-binding Proteins
regulate operator genes
(turn them on, off, up,
down)
Gene Expression
Epigenetics
Epigenetics
DNA-Binding Proteins
• Epigenomes do not affect
Methylation – turn genes off
DNA, but are heritable (can
Histone Acetylation – turn
be passed on to at least one
genes on
generation)
Gene Expression
Final Thoughts
The Environment:
• Cannot alter the genes you have
• Can alter the expression of the genes you have
• Can alter your epigenome
• And your epigenome IS heritable
• Thus, environmental influences of genetic
expression ARE heritable, but only through the
EPIGENOME
Factors that Influence Epigenetic Patterns
• Prenatal environment (nutrition, hormones, etc)
• Smoking
• Diet
• Stress
• Physical activity
• Epigenetic drift – naturally occurring changes through
successive cell divisions
Video
http://www.pbs.org/wgbh/nova/body/epigenetics.html
Behavioral Development: Gene-Environment
Interaction
Maze-Bright, Maze-Dull Rats
• Tyron (1934)
demonstrated that traits
can be selectively bred
• Trained heterogeneous
group of rats
• Mated rats with least
mistakes and ones with
most mistakes (for many
generations)
• By 8th gen. almost no
overlap between groups
• Included cross-fostering
control
• Are there any potential confounds to this study?
Behavioral Development: Gene-Environment
Interaction
Maze-Bright, Maze-Dull Rats
Confound 1: Parenting
Cross-fostering: Maze-bright offspring raised by mazedull parents
Confound 2: Extraneous traits
• Searle (1949) tested rats on 30 dif. behavioral tests
• Maze-dull rats not less intelligent, but more emotional
Behavioral Development: Gene-Environment
Interaction
Maze-Bright, Maze-Dull Rats
Gene-Environment Interaction
• Both groups raised in:
*Enriched environment
*Impoverished environment
Behavioral Development: Gene-Environment
Interaction
Maze-Bright, Maze-Dull Rats
Gene-Environment Interaction
• Both groups raised in
*Enriched environment
*Impoverished environment
• Both groups performed equally
well when raised in an enriched
environment