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Summary (BLOA) IB Psychology notes: Genetics and Behavior
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Not the best set of notes I've ever written but got me a 7. Maybe you'll find something idk
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Genetics and Behavior___ = SAQ Studies
Genetics can influence our behavior and vice versa.
Genetics and influence our biology which can influence our behavior.
Inherited part of an individual’s psychological diathesis. Influences the potential for a behavior
but cannot determine cause and effect relationship as genetics do not directly influence behavior
but rather does do in an indirect manner by regulating, for example, neurotransmission or other
biological processes in the brain.
** Genes are switched on and off by signals from inside and outside the body. Internal
signals include the presence of hormones or other chemicals, or indeed other genes.
Hormones are frequently produced as a result of environmental events and work by
altering gene expression. There are countless environmental events that also affect
gene expression. The signal activates special proteins that can promote or block the
expression of a gene. Genes are constantly being switched on and off.
Sometimes genes are permanently switched off. This is mostly achieved by methylation
of the DNA molecule as part of the developmental process.
This effect on genes is sometimes referred to as epigenetics as there is no alteration in
the actual structure of the DNA. Mutations occur when there is an actual alteration of
the DNA.
1.Genes and behaviour
Genes are made up of DNA which provides the blueprint for the structure and function of the
human body. This could include behaviour. An individual’s genome refers to all the genes that
an individual possesses. Not all genes an individual possesses are expressed at all times. Genes
can be switched on and off. This is gene regulation resulting in differential gene expression.
Therefore, having a gene for a particular behaviour does not necessarily mean that an individual
will exhibit that behaviour. This is usually done through environmental stimuli. Eg. trauma
exposure or childhood abuse.
1.1 Genes and PTSD
Genetics determine hippocampal volume to a degree. Also, it determines amygdala shape and
function to a degree as well. Does genetics influence the susceptibility of an individual to PTSD?
Etiology: cause or set of causes of a disease or disorder.
Commonly cited biological etiologies of PTSD:
- Hippocampal atrophy
- Hyperresponsive amygdala.
, Are brain abnormalities a symptom or etiology of PTSD?
Case-control design.
- A study that compares patients who have a disease or outcome of interest (cases) with
patients who do not have the disease or outcome (controls), and looks back
retrospectively to compare how frequently the exposure to a risk factor is present in each
group to determine the relationship between the risk factor and the disease.
Gilbertson et al. (2002)
Aim:
To investigate and to provide insight as to whether or not the difference in brain structure is a
risk factor for PTSD.
Method:
Case-control study on 34 sets of identical twins (monozygotic). Monozygotic twins have 100%
of their DNA in common. If they have been raised in the same household, they’ve probably had
similar upbringing and thus similar experiences.
They used two different types of identical twins. One set of twins has one twin who has gone to
war and developed PTSD (trauma exposed). These twins were compared to a second set of
twins. The second set was the same as the first, except the twin that went away to war (trauma
exposure) did not develop PTSD. The hippocampal volumes of the twins were compared.
Results:
The trauma unexposed twins of veterans with PTSD had smaller hippocampal volumes
compared to unexposed twins of veterans without PTSD.
The fact that the co-twin of the PTSD patient had a smaller hippocampus compared to the co-
twin of the non-PTSD veteran, suggests that the low hippocampal volume is a factor that
increases the vulnerability to developing PTSD. Therefore, the low hippocampal volume may be
an existing facto in an individual that might increase their vulnerability to developing PTSD as a
result of exposure to trauma.
1.2 Genes and Aggression (MAOA Gene)
The MAOA gene codes for the MAOA enzyme which is an enzyme that affects the levels of
neurotransmitters, specifically serotonin. Some people have a mutation in this gene so they don’t
produce enough of this enzyme, and so the levels of neurotransmitters in their brain are affected.
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