PSYA01H3 Chapter Notes - Chapter 3: Behavioural Genetics, Gene Expression, Heredity
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Chapter 3: Biological Psychology
3.1: Genetic and Evolutionary Perspectives on Behaviour
Heredity and behaviour:
Research has made it clear that behaviours are influenced by genes just as physical characteristics
are, as the two are often related.
Genetic material is organized into genes- basic units of heredity, are responsible for guiding the
process of creating the proteins that make up our physical structures and regulate development
and physiological processes throughout the lifespan.
Genes are made of segments of DNA, a molecule formed in a double-helix shape that contains four
nucleotides: A, C, G, and T.
Genotype- unique set of genes that comprise that individual’s genetic code.
Phenotype- the physical traits or behavioural characteristics that show genetic variation, such as
eye colour, the shape and size of facial features, and even personality.
Genes are organized in pairs along chromosomes, structures in the cellular nucleus that are lined
with all of the genes an individual inherits.
Behavioural genomics – study of DNA and the ways in which specific genes are related to
behaviour.
Behavioural genetics is the study of how genes and the environment influence behaviour.
Twins provide the most insight into the genetic effects on behaviour.
Monozygotic twins come from a single ovum (egg), which makes them genetically identical.
Dizygotic twins (fraternal twins) come from two separate eyes fertilized by two different sperm
cells that share the same womb; these twins have approximately 50% of their genetics in common.
Heritability – a statistic, expressed as a number between zero and one that represents the degree
to which genetic differences between individuals contribute to individual differences in a
behaviour or trait found in a population.
Nature and nurture interact to produce behaviour.
Between 6000 and 7000 genes are active in the human brain, which influence the development of
different brain structures, the production of chemicals that allow brain cells to communicate with
each other, and the refinement of connections between cells that allow large-scale brain networks
to form.
If some genes fail to be activated properly, people may be at a greater risk for developing brain-
related disorders
Epigenetics – study of changes in gene expression that occur as a result of experience and that do
not alter the genetic code.
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