I. Behavioral Traits:
How a person communicates,
Copes with rage,
Disorders with behavioral symptoms:
Most behavioral disorders affect more than 1 in
individuals and are caused by several genes and the
They are common, polygenetic and multifactorial.
II. Tools to study behaviour genetics:
Adoptee and twin studies;
New approaches: 1.
studies that correlate genetic markers such as SNP (single
nucleotide polymorphism) patterns with particular symptoms.
2. Analysis of mutations in specific candidate genes that are
exclusively in individuals with the bahaviour.
III. Behavioral genetics: A study of nervous system variation and function. Genes control the synthesis, levels, and distribution of neurotransmitters, which are the chemical messengers that connect nerve cells (neurons) into pathways. Signal transduction is also a key part of the function of the nervous system.
IV. Examples of behavioral genetic traits:
(attention deficit hyperactivity disorder) has a
of H = 0.8. Linked to the
function of a neurotansmitter --- dopamine.
Individual does not speak or interact with others and is
restricted or repetitive behaviours. Heritability of 0.6 ~ 0.9.
Anorexia nervosa. H = 0.5 ~ 0.8
high risk genes include those traits that control the traits of perfectionism,
orderliness, low tolerance for new situation, maturity fears, low
self-estemm, and overall anxiety.
Sleep: disorder called: "narcolepsy with cataplexy"
Narcolepsy: Produces daytime sleepiness and the tendency to fall asleep very rapidly, serveral times a day.
Cataplexy: A short episodes of muscle weakness, during
which the jaw sags, head drops, knees buckle, and the
person falls to ground.
H = 0.25 ~ 0.31
Familial advanced sleep phase syndrome (FASPS):
Intelligence: the ability to reason, learn, remember, connect ideas, deduce and create.
H = 0.8
In 1904, Alfred Binet developed a test with verbal, numerical, and pictorial questions, and
then modified at Stanford University. Called "Intelligence Quotient" - IQ
An average score on IQ
is 100, two-thirds of all people scoring between 85 and 115.
Drug Addiction: The compulsive behavior of seeking and taking a drug despite knowing its
Two identifying characteristics:
1. Tolerance: the
take more of the drug to achieve the same effects as time goes
2. Dependence: the onset of withdrawal symptoms when a person ceases taking the drug.
produces stable, rather than temporary, brain damages.
H = 0.4 ~ 0.6
Human equivalents of the opiates are the endorphins and enkephalins, which are
equivalent to plant-derived chemicals, cocaine, opium, and tetrahydrocannabinol (THC).
Alcohol dehydrogenase, and an allele of the gene that encodes the dopamine D(2)
receptor. High percentage people with alcoholism are homozygous for the A1 allele of
D(2) dopamine receptor gene.
H = 0.4 ~ 0.6
Bipolar affective disorder: H = 0.8
Serotonin --- neurotransmitter
loss of the ability to organize thoughts and perceptions, which leads
withdrawal from reality.
H = 0.8