biological explanation of schizophrenia (genes) Flashcards
How is Di-George syndrome caused?
caused by deletion of 30-40 neighbouring genes located in a specific region of chromosome 22.
what is the percentage of people with Di-George syndrome that go on to develop schizophrenia?
25%
What are the two genes that are linked to the presence of schizophrenia?
COMT gene
DISC1 gene
Describe the COMT gene and how it can cause SZ
link between di-george syndrome and SZ may be due to deletion of this gene
this genes provides code for catechol-O-menthytransferase, enzyme that breaks down dopamine
Deletion of COMT therefore means less enzyme breaking down dopamine, so excess dopamine leading to SZ
describe the study that supports the idea that DISC1 gene causes SZ hint: kim et al
Kim et al (2012) people with an abnormality in DISC1 gene are 1.4x likely to develop SZ than people without this abnormality
describe the diathesis stress model
It is the idea that genes cause a vulnerability for SZ rather than being a cause of it. You may have SZ genes (diathesis) but can only be triggered by the environment effects.
The ‘stress’ part of the model was seen as psychological in nature e.g. harsh parenting, cannabis use which interferes with dopamine system
a strength of genetic explanation of schizophrenia (Gottesman)
they analysed concordance rates of MZ and DZ twins and found clear relationship between genetic similarity and an increase in two related people both having SZ. Concordance rate of MZ 42% and DZ 9%. This suggests that although SZ is not entirely genetic disorder, shows biology plays significant part.
competing argument against gottesman’s support of genetic explanation of SZ
MZ twins are likely to be treated more similarly due to similar appearance and the fact they are same sex. This reduces validity of conclusion that the greater amount of shared DNA is responsible for their similar pathology.
a weakness is the fact that concordance rate is far from 100% even for MZ twins, describe a study to support this weakness.
studies showed showed the longer a person is exposed to city life, the greater the risk of SZ, = suggests that rural dwelling may help protect a person from developing a disorder to which they are genetically predisposed.
describe research evidence to support COMT gene as link to SZ hint: hayley’s mum names.
Michael egan et al (2001) proposed a link between decreased dopamine activity and a form of COMT gene called ‘Val’ allele . They concluded that inheriting two copies of the Val allele from each parent increases risk of SZ by 50%
Describe how genes linking to SZ can be applied to society
application to genetic counselling - a strength of the genetic approach to schizophrenia is that it has been use to inform genetic counselling. When a family member gets SZ, they may want to be informed whether condition is heritable. ‘Recurrence risk’ can be calculated which can provide support for families during difficult times. It can help to allay the fears of inevitability of SZ, while also helping making rational choices about family planning.
