Cause

Question 1

What is the cause?

Answer 1

It is still unknown, but heritability and genetics plays a role

Question 2

What have twin studies revealed?

Answer 2

It is a heritable trait, but it is not due to a single dominant of recessive gene - there has been no single gene shown to cause schizophrenia, several genes are involved

Question 3

What does having a schizophrenia gene mean?

Answer 3

More susceptible to developing it - triggered by other factors

Question 4

How do we know genes are involved?

Answer 4

Greater chance of relatives having schizophrenia if you have it

Question 5

What mutation is involved?

Answer 5

DISC1 - disrupted in schizophrenia 1
involved in the regulation of neurogenesis, neuronal migration, post synaptic density in excitatory neurons and mitochondria function - its presence appears to increase the chance of developing it by a factor of 50
but it also increases other mental disorders, including bipolar, mood disorder and autism

Question 6

How many genes have been identified?

Answer 6

More than 100 genes associated with the susceptibility for it

Question 7

Do parents have an impact?

Answer 7

Paternal age provides evidence that genetic mutations impact development

Question 8

What is the impact of paternal age?

Answer 8

Children of older fathers are more likely to develop schizohprenia

Question 9

Why does paternal age impact?

Answer 9

More chances of getting a mutation - mutations in the spermatocytes (cells that produce sperm)
following puberty, these divide every 16 days, which means they have divided 540 times by 35

Question 10

When are chromosomal abnormalities more likely?

Answer 10

As you get older

Question 11

What are spermatocytes?

Answer 11

The cells that produce sperm

Question 12

Why does maternal age not impact?

Answer 12

Women oocytes divide 23 times before birth and only one after that

Question 13

Percent developing schizophrenia

Answer 13

General pop - 1%
husband/wife - 2%
cousin 2%
children 13%
siblings 9%
DZ twins 17%
parents 6%
MZ twins 48%
children of two schizophrenia parents 46%
genetic component but not the whole story

Question 14

What do MZ twins share?

Answer 14

They are genetically identical, and share the same intrauterine environment - but the prenatal environment isn’t always identical

Question 15

How is it possible that the parental environment of MZ twins is not always identical?

Answer 15

There are two types of twins:
Monochorionic
Dichorionic

Question 16

When does the formation of MZ twins occur?

Answer 16

When the blastocyst splits into two - to get two identical babies, needs to be a split of a zygote

Question 17

What is the difference between monochorionic and dichorionic twins?

Answer 17

Monochorionic - if blastocyst splits into two after day 4, share a single placenta

Dichorionic - if it occurs before day 4, two organisms develop independently, forming own placenta

Question 18

What are the concordance rates for MZ twins?

Answer 18

Dichorionic - 11%

Monochorionic - 60% - the more they share, the higher changes to get it