•What is heritability, how do we study it (what are twin and adoption
studies…what do their results tell us?), and what are the problems with
Estimate of how much of the variance in a characteristic (within a population) is due
to differences in heredity (genes)
We study it with twin studies:
Identical twins (monozygotic)> fraternal twins (dizygotic) -> high
Identical twins (monozygotic) = fraternal twins (dizygotic) -> low heritability
Also with twin studies
-if adopted kids resemble biological parents more than adoptive parents we
assume high heritability
•What are examples of environmental influences on traits with otherwise high
–MZ twins share chorion and blood supply (ie, more similar prenatal
environment compared to DZ twins)
–…so could be genetics or could be prenatal environment
–Biological children of low IQ or mentally ill parents tend to have
similar problems even if raised by “great” adoptive parents.
–…could be genetics…BUT could be reflection of poor prenatal
-inherited or genetic does not necessarily equal unmodifiable (although
sometimes it does)
Elevated plus maze: some genetic strains tend to stay in walled arms; others
venture out onto open arms. BUT sometimes a strain that is unadventurous in one
lab is more adventurous in another. Depends on exactly how the researchers handle
the mice, maybe odors in the room…
PKU: genetic inability to metabolize phenylalenine. If untreated, PKU
accumulates to toxic levels impairs brain development, children are mentally
retarded, restless, irritable; This is caused by recessive gene (1% of Europeans carry
it). In babies with high levels of phenylalenine in blood or urine, diets low in
phenylalenine can minimize brain damage. Have to stay on diet for life, and PKU
moms have to be very careful in pregnancy. Difficult diet (avoid eggs, meat, dairy,
grains, aspartame, which is 50% phenylalenine!)
•What is a sex-linked gene? Understand the heritability of sex-linked genes.
What is a sex-limited gene? What are examples of each (sex-linked and sex-
-genes on sex chromosomes (male XY, female XX)
-if male get this gene, he will display trait
-female has to get it on both X to display, if on 1 she is carrier -disorders by sex linked genes more common in males
*rest of chromosomes called autosomal
-present in both sexes but has an effect only (mostly) in one sex
-genes for chest hair (men); breast size (women)
-genes are “turned on” under the influence of sex hormones
-fragile X syndrome
-red green color blindness
-duchenne muscular dystrophy
•What is the multiplier effect?
Genes predispose you to behaviors and to different treatment by others
Examples) temper tantrums; attractiveness; athletics
-What started out as potentially small effect of genes ends up having a huge
behavioral result …leading to an overestimation of heritability!
•Terms to know and understand: DNA, RNA, gene, chromosome, transcription,
translation, homozygous, heterozygous, dominant, recessive,
DNA: deoxynucleic acid; double stranded chemical;In DNA, the purine bases are
adenine and guanine, while the pyrimidines are thymine and cytosine. RNA uses
uracil in place of thymine.
RNAI: single stranded chemical; template for protein (work horse of body)
Gene: sequences of DNA code for proteins, portion of DNA; template for RNA
Chromosome: contain DNA
Transcription is the synthesis of mRNA from a DNA template.
Translation is the process where ribosomes synthesize proteins using the
mature mRNA transcript produced during transcription.
Homozygous :person with identical set of genes on the 2 chromosomes is
Heterozygous: person with unmatched pair of genes on the 2 matched
chromosomes is heterozygous for that gene
Dominant: a gene that shows strong effect in heterozygous or homozygous
condition; tongue rolling dominant, huntington’s disease
Recessive: a gene that shows strong effect only in homozygous condition; attached
•What is evolution? What types of traits move on to the next generation?
What is natural selection? What is artificial selection? Why did Darwin prefer
“decent with modification” to “evolution”?
-changes over generations in the frequencies of various genes in a population
-only heritable traits move on to the next generation; acquired traits are not
inherited (kind of)
-natural selection: if certain individuals are more successful live to
reproductive age their genes will become more prevalent –For a gene to go on to next generation, carrier must reproduce, BUT what is
beneficial for reproduction in one generation, might not be beneficial later
(peacock’s tail, peppered moth)
•What is epigenetics? Why does this new field of research “blur the line
between environment and genetics”?
•Epigenetics: changes in phenotype (appearance) or gene expression caused
by mechanisms other than changes in the underlying DNA sequence
•For example, a methyl group (CH3) can attach itself to a gene and inactivate
it. The inactivated gene is passed down.
•Early experience like malnutrition or extreme stress can cause this
•Behavioral changes in rats based on things that happened to mom or
•Evidence in humans of health being affected by the health of the
grandparents (as children!) (which blurs line)
-These changes may remain through cell divisions for the remainder of the
cell's life and may also last for multiple generations.
However, there is no change in the underlying DNA sequence of the organism
instead, non-genetic factors cause the organism's genes to behave (or "express
•DNA is wrapped around a histone core. Things (acetyl groups, methyl
groups, etc) can get into the structure and loosen or tighten the wound-up DNA.
This will make a gene more or less likely to be expressed. AND these changes are
heritable. SO you can alter the probability that a gene will be expressed without
actually altering the DNA itself.
Cells of the Nervous System
o •Know the different organelles and their functions.
o Nucleus: DNA
o ER: rough for translation; smooth for transport/modification of new
o Golgi: finishing touches on new proteins
o Mitrochondria: energy production
o Lysosome: clean-up
o Plasma membrane: semipermeable lipid bilayer (next slide)
o •Understand the structure of the cell membrane.
o phospholipid bilayer: 2 layers of fat molecules that are free to float
around eachother; semipermeable
water, oxygen, carbon dioxide move freely
most chemicals cannot cross cell membrane
o •Know the parts of a neuron and their functions. Be able to label the
parts of a neuron.
o Groups of neurons called nucleus
o Basic unit of nervous system
o Cells that receive and transmit info o Many neurological diseases are due to damage of group of neurons
o Receives nerve impulses through its dendrites, sends impulses
through its axon to the terminal buttons where neurotransmitters are
released to stimulate other neurons
o •Compare motor neurons & sensory neurons: How are they different
from each other & how are they the same? Be able to draw each one.
Which one is multipolar and which one is unipolar?
o Motor Neuron
Cell body (soma) lives in
the spinal cord
Axon is part of a nerve in
your body, terminals are in your
o Somatosensory (touch) neuron
Soma lives just outside
the spinal cord (in a dorsal root
Most of its length is an
endings in the skin, and its
terminals are in the spinal
o •Know the different
types of glial cells and their functions. ESPECIALLY which one puts
myelin on axons in the CNS and which one myelinates axons of the PNS?
o Glial cells do not transmit info over long distances
o Do not exchange chemicals, nutrients with neurons; NMDA receptors
Astrocytes= wrap around terminals of related axons, remove
waste material, dilate blood vessels in active regions of brain,
BBB** Oligodendrocytes =myelin in CNS
Schwann cells =myelin in PNS
Microglia =repair (remove waste, fungi, microorganisms)
function unknown in healthy brain. When there is damage, the
microglia proliferate, migrate to the point of damage, turn into
macrophages, and devour debris and pathogens.
Radial glia =guide cell & axon migration during development;
after development turn into neurons; one in white matter one
type in gray matter (type of astrocyte)
o When a PNS nerve is cut, the axons regrow thru the Schwann cell tube,
o •Know the parts of a synapse (presynaptic cell (terminal), postsynaptic
cell (dendrite or dendritic spine), synaptic cleft).
o Synapse: where two cells meet
o Info is going from Presynaptic synaptic cleft/gap postsynaptic
o Cell conducts action potential from soma to terminal, then terminal
releases chemicals that cross cleft and go to dendrites on postsynaptic
o •Understand the terms afferent and efferent.
o •What/where is the blood brain barrier? What does it keep out, let in?
What are the implications of this for drug use and medicine?
o Endothelial cells w/tight junctions surrounding cappilaries;
astrocytes surround endothelial cells
o BBB keeps out
Viruses and bacteria
o BBB lets through
Small uncharged molecules
Small uncharged molecules (O2, CO2). Also H2O gets thru
using a special channel Molecules that dissolve in fats of capillary walls (psychiatric
drugs like antidepressants & drugs of abuse like heroin and
marijuana & some vitamins like A and D)
o some viruses do enter (herpes thru cells spinal cord) chickenpox,
shingles, genital herpes
o Some areas have inc. BBB on purpose
o Active transport used to get nutrients to brain
o Barrier keeps out useful nutrition
o Which are more numerous, neurons or glia?
o •8.5-10x more glia than neurons!
Resting potential and action potential
o •What ions are important in the action potential? When the cell is at
rest, which ions are most highly concentrated inside of the cell, and
which ones are most highly concentrated outside of the cell?
o Na+, Ca2+, K+, Cl-
o The inside of the neuron is more negatively charged than the outside
of the neuron and the neuron is said to be polarized
Prepares neuron for action potential
o Sodium is more than ten times more concentrated outside the
neuron’s membrane than inside the neuron; Cl is more concentrated
o K+ is more concentrated inside
o •Understand the forces working on the ions (electrical gradient and
o The C