PSYA01H3 Chapter Notes - Chapter 3: Twin Study, Behavioural Genetics, Gene Expression
Chapter 3:
1.1 genetic and evolutionary perspective on behavior:
Genetic codes:
• are found in the nucleus of most of the billions of cells in the human body
• Genetic material is organized into genes, which is the basic units of heredity
Genes: are responsible for guiding the process of creating the protein that make up our physical
structures and regulate development and physiological processes throughout the lifespan
• Composed of segments of DNA (deoxyribonucleic acid) which is a molecule formed in a
double helix shape that contains four nucleotides (a, c, g, t)
• Four nucleotides are the genetic makeup of an organism – the unique set of genes that
comprise that individuals genetic code
• Genotype: the genetic make of an organism, the unique set of genes that comprise that
individuals genetic code
• Phenotype: the physical traits or behavioral characteristics that show genetic variation
such as eye colour, the shape and size of facial features and personality
• Chromosomes: structure in the cellular nucleus that are lined with all of genes an
individual inherits, humans have about 23 chromosomes and down syndrome is the
trisomy on the 21st chromosome
• Homozygous: when 2 corresponding genes at a given location on a pair of
chromosomes are the same
• Heterozygous: if the two genes differ
Behavioral genomics: the study of DNA and the ways in which specific genes are related to
behaviour
• Behavioral genetics: is the study of how genes and the environment influence
behaviour
• Monozygotic twins come from a single egg which makes them genetically
identical
• Dizygotic twins (fraternal twins) come from two separate eggs fertilized by two
different sperm cells that share the womb; these twins have approximately 50
percent of their genetics in common
• Behavioral genetics use twin studies to calculate heritability – a statistic,
expressed as number between zero and one that represent the degree to which
genetic differences between individuals contribute to individual differences in
behaviour or trait found in the population
Epigenetics: The study of changes in gene expression that occur as a result of experience and
that do not alter the genetic code is known as
• Gene expression is a life process, factors such as diet, stress levels and sleep can
influence whether genes are turned on or off
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• Serotonin: is a brain chemical related to mood, and imbalances of it are associated with
depression
Diathesis-stress model for psychological disorders: the interaction between a genetic
predisposing for a disorder and life stress
Darwi’s theory of atural selectio: process by which favourable traits become increasingly
common a population of interbreeding individuals, while traits that are unfavourable become
less common
Evolution: change in the frequency of genes occurring in an interbreeding population over
generation
• Evolutionary Psychology: attempts to explain human behaviours based on the
beneficial function they may have served in our species development
Intrasexual selection: is a situation in which members of the same sex competes in order to win
the opportunity to mate with members of the opposite sex
Intersexual selection: is a situation in which members of one sex select a mating partner based
on their desirable traits
• Homo habilis: handy man, first of our ancestors to use stone tools
• Homo erectis: erect man, based on ability to walk upright
• Homo sapiens: wise man, larger brains than those of homo erectis
Three reasons why human brains are more powerful than any other:
1. Cerebral cortex: the location of the most of our advanced cognitive abilities
2. Frontal lobes: critical for our ability to form plans, solve problems, make decisions and
control our attention and actions among other functions. Front third of brain is more
developed
3. Neotony: allows humans to develop large a large brain while limiting the physical
damage associated with the baby exiting the narrow birth canal
Hunter – Gatherer theory: links performance on specific tasks to the different roles performed
on specific tasks to the different roles performance by male and females over the course of our
evolutionary history
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3.2; How the nervous system works: cells and neurotransmitter
Neurons: one of the major types of cells in the nervous system that are responsible for sending
and receiving messages throughout the body
• All euros hae a ell ody soa, hih otais the uleus that houses the ell’s
genetic material
• Dendrites: small branches radiating from the cell body that receive messages from
other cells and transmit the message toward the cell body
Axon: the structure that transports information from the neuron to neighboring neurons in the
form of the electrochemical reactions, at the end of the axons are axon terminals
• Located within the axon terminals are chemicals called neurotransmitters, the
chemical that function as messengers allowing neurons to communicate with
each other
• Neurotransmitters are released across synapses, the microscopically small
spaces that separate individual nerve cells.
• Neurons differ in form and function
• Sensory neurons: fetch information from the bodily sense and bring it towards the brains
Glial cells:
• Myelin is a fatty sheath that insulates axons from one another, resulting in increased
speed and efficiency of neural
• communication.o Myelin is made from a highly abundant type of cell called glia (Greek
for glue.o Glial cells are specialized cells of the nervous system that are involved in
mounting immune responses in the brain,
• removing wastes, and synchronizing activity of the billions of neurons that constitute
the nervous system
The Neuro’s Electrical Syste: Restig ad Action Potentials: The inner and outer
environments of a neuron differ in their concentrations of charged atoms called ions. In other
words, the neuron is polarized.
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