• Biological Perspective – focuses on the interaction between behavior and organic functions.
• Chromosomes – mass of threadlike structures in cells. Contain coded information of all the
instructions, inherited from the parents at the moment of conception, as to what proteins the
body should produce. These proteins determine your physical characteristics.
• Gene – individual unit that carries genetic information. There are more than 2000 genes on a
• Polygenic – traits resulting from the interaction of many genes.
• Diathesis-Stress Model – certain genes or gene combinations produce a diathesis, or
constitutional predisposition, to a disorder. If this diathesis is then combined with certain
kinds of environmental stress, abnormal behavior will result.
• Genotype – a highly individual combination of genes representing the biological inheritance
from the parents. This genotype interacts with the person’s environment to determine the
• Phenotype – the person’s equally unique combination of observable characteristics.
• The entire purpose of behavior genetics is to discover to what extent different psychological
disorders are due to genetic inheritance rather than environmental influence. This is done via
three basic types of studies:
1) Family Studies – different types of family relationships involve different degrees of genetic
similarity. The genetic researcher puts together a substantial sample of families containing
one diagnosed case, referred to as the index case.
2) Twin Studies – basic technique is to compare monozygotic and dizygotic twins.
Monozygotic twins - (identical twins) develop from a single fertilized egg and therefore
have exactly the
same genotype. They always the same sex, have the same eye
color, share the same
blood type, etc.
Dizygotic twins - (fraternal twins) develop from two eggs, fertilized by two different
sperm. Like any
other siblings, have only appx 50% of their genes in common.
Concordant - twins used in research that share the same disorder. If the researcher
should discover that
the concordance rate for the MZ twins is considerably greater than that
for the DZ twins,
then this would be substantial evidence that predisposition to the
disorder is genetically
3) Adoption Studies – represent an attempt tat decisively separating the evidence of genetic
influence from that of environmental influence. Studying the results of siblings separated at
birth by adoption, as opposed to those raised together, in order to eliminate the ‘environment’
1 • Nervous System – a vast electro-chemical conducting network that extends from the brain
through the rest of the body. Its function is to transmit information, in the form of electro-
chemical impulses, among various cells throughout the body.
• Central Nervous System – Headquarters for the Nervous System. Consists of the brain and
spinal cord. Primarily responsible for the storage and transmission of information.
• Neurons – nerve cells that make up the nervous system. They have the following
characteristic structure and features:
A) Cell Body – contains the nucleus. The chemical reaction that take place here, provide
B) Dendrites – short fibers branching out from the cell body. Receive impulse from other
C) Axon – long fiber stretching outward from the cell body. Transmit impulses to other
D) Axon Terminals – the axon’s branchlike endings, with button-like structures at the
E) Myelin Sheath – made up of fatty cells wrapped around the axon in segments. S