Schizophrenia- Biological Genetics

Question 1

What does this theory suggest?

Answer 1

This explanation believes that’s SZ is inherited via genetics passed down through families
-The closer family relationship the greater risk of SZ developing
-First degree relatives share 50% of DNA with genes

Question 2

Family studys- Gottesman heriabilty of SZ categorys?

Answer 2

100% of gene MZ- 48% shared gene
First degree relative 50% DZ- 17%
Children- 9%
Parent + Sibling- 6%

Question 3

What does Gottesmans study show?

Answer 3

Identical twins have a high likelihood for MZ twins to have a shared gene
But with parents, siblings and DZ twins less of a shared gene
Suggesting a correlation

Question 4

Twin study- Gottesman and Shields?

Answer 4

Concordance rate of 42% of MZ and 9% for DZ

Question 5

Twin study- Cardno et al?

Answer 5

Found 40% of concordance rate in MZ twins compared with 5.3% in DZ twins

Question 6

Adoption studies- Heston?

Answer 6

Compared 47 children of SZ mother who were adopted before the age of 1 month with a control group of 47 children raised by non SZ mothers
10% of children with SZ mothers developed SZ themselves whereas none of children from control group did

Question 7

Adoption studies- Tienari et al?

Answer 7

Compared 112 cases of adopted children who had biological mothers who had been diagnosed with SZ with 135 adopted children who had non SZ biological mothers
7% of thee children 112 developed SZ compared to 1.5% of control group

Question 8

Are adoption studies consistent?

Answer 8

Yes both show a similar number of those adopted vs those who developed SZ and those that didn’t

Question 9

Candidate genes- what can be said about genes?

Answer 9

SZ is polygenic (many genes)
Aetiologically heterogeneous (caused by combinations of genes)
-Can include dopamine

Question 10

Gene- what’s one gene relating to SZ?

Answer 10

Complement component 4 C4

Question 11

What have researchers found about SZ?

Answer 11

Harvard and MIT identified a gene they believe increases risk of SZ
After conducting studies on mice and humans researchers said this new SZ risk gene (C4) appears to be involved in eliminating the connections between neurons
This is called synaptic pruning happening in teenage years

Question 12

What is synaptic pruning?

Answer 12

The process of eliminating unused synapses to increase efficiency in your brain

Question 13

How does synaptic pruning explain SZ?

Answer 13

Excessive or inappropriate pruning of neitra connections could lead to the development of SZ which would explain why SZ symptoms first appear in adolescence

Question 14

Eval- research support Varma et al?

Answer 14

Looked at first degree relatives of approximately 100 patients with SZ and 1000 controls
Psychiatric illness was found in 16% of the FDRs of patients with SZ compared to 7% of the controls, suggesting link between SZ and genetics

Question 15

Eval- research support Claridge and Davis?

Answer 15

Reviewed twin studies into component to the disorder reporting that concordance rates for MZ twins ranging from 0% to 90%, generally is 50%
So if one MZ twin had SZ there’s a 50/50 chance the other twin will develop the disorder

Question 16

Research support- Gottesman?

Answer 16

Concordance rate of 42% of MZ and 9% for DZ
If SZ is caused by genetics you would expect concordance rares to be high in MZ twins then DZ which it is

Question 17

Eval- counter argument by Gottesman?

Answer 17

Torey
Reassessed 8 early studies that the concordance rates for MZ twins was 26% compared to 6% for DZ twins
This is not consistent with previous findings (48/17%)

Question 18

Evaluation- benefits of adoption studies?

Answer 18

Looks into nature and nurture
Tienari et al- 164 adoptees whose biological mothers had been diagnosed with SZ. Found that 6.7% also received a diagnosis of SZ vs 2% of the control adoptees born to non SZ mothers

Question 19

Evaluation- Polygenic O’Donavan et al?

Answer 19

SZ dominated by different genes
-108 specific locations in the human gene linked to SZ

Question 20

Evaluation- Polygenic counter argument?

Answer 20

Even though the potential gene involved in SZ may have been identified, how they actually cause the illness is unknown as yet

Question 21

Diathesis stress model?

Answer 21

Gene needs to be triggered be a stress factor
More then just genetics