genetic explanation of SZ

Answer 1

There is a strong heritable factor in the development of the disorder.(AO1) Twins share the same pre-natal and post-natal environment so this may contribute to the increased chance of both developing the disorder, not just shared genes. The mothers health and factors like diet, smoking etc can affect the development in the womb.(AO3)

Answer 2

There is less than 1% risk of developing the disorder in the general population but this increases to between 2-6% if you have a 2nd ° relative with the disorder This increases further to between 6-17% if you have a 1st ° relative with Sz.(AO1) The higher incidence in families could be due to the shared environment rather than shared genes; research into dysfunctional families communication patterns and schizophrenic relapse rates suggests that schizophrenia is the result of stress caused by negative emotions within families. (AO3)

Answer 3

If you have a MZ twin with the disorder your risk increases to around 48% - around 17% for DZ (AO1) However, the concordance rate for MZ twins is only 48% as these twins are genetically identical you would expect it to be 100%, suggesting the illness is not purely attributed to genetic factors there must be other factors involved (as MZ twins share 100% of their genes).(AO3)

Answer 4

The greater the genetic relatedness the higher the risk of developing the disorder.(AO1) Tienari 2000 found that 7% of adopted children with schizophrenia had a biological mother with the disorder, whereas only 2% of adopted children with non-schizophrenic biological mothers developed the disorder, supporting the role of genes in schizophrenia.(AO3) However, adopted children are often placed in families with similar backgrounds and families are often aware of the mother’s schizophrenia so we still cannot completely separate nature and nurture.(AO3)

Answer 5

Harrison and Weinberger ‘04 - could be the result of genes effect on the functions of synapses and brain circuitry, so it is this effect that causes the development of schizophrenic symptoms.(AO1)

Question 6

conclusion

Answer 6

in conclusion according to the Diathesis Stress theory It is likely to be due to a combination of up to 6 different genes rather than a single gene.