Lecture 3 – Behavioural Genetics
Some important concepts
– Genes and environment work together and affect one another
– sometimes environment matters more, ex. Personality, where concordance is around 30-
– Concordance – the presence of the same trait in both members of a pair of twins
– Epigenetics – genes do code for certain environment reactions, but environment can actually
alter your genes. Your genotype can be altered by environment. This can actually be passed
on to offspring as well
– Genotype – set of genes that you've inherited
– Phenotype – how you express your genotype
– ex. genotype for height, but raised with decreased nutrition, may never as be tall as you
were to be. Phenotype and Genotype can be different
– Ex. height changes in japan, used to be short, but suddenly japanese people were becoming
taller (related to nutrition?)
– ex. psychiatric disorders...you are more likely to express these disorders when you were in a
type of environment that made the expression more likely
– Caspi et al.....Study that looked at depression. These authors were interested in gene and
environment. Identified gene for serotonin levels. Serotonin transporter gene. You have
lower levels if expressed a certain way.
– Some subjects had this, some didn't
– Then looked at life events (married, pet died)
– Does this gene depict depression, or does it start with stressful events?
– Having this gene does not cause depression if there are no stressful life events that
– However, people who had this gene and experienced life events were more likely to be
– Ex. Intelligence
– 1958 study on rats. Cooper experimentalist. Some rats were good at learning mazes.
Some rats not so bright
– Maze bright vs. maze dull rats
– You can actually breed for intelligence in rats by mating maze bright vs dull rats
– Raised rats were put into different environments. Good environment, enriched
environment (full of social and perceptual stimuli). Impoverished environment.
– In enriched environment, maze dull rats caught up really fast.
– In good, maze bright still better
– Impoverished, maze bright similar to maze dull
– Achange of 20IQ can occur based on rearing environment
Genes and complex traits
– Is there a gene for intelligence?
– Polygenic (aka multigenic) inheritance – multiple genes responsible
– Harder to research
– Can we disentangle the effects of genes and environment on multigenic traits?