Genetic Explanation

Question 1

Why are twins used to test genetics on S?

Answer 1

MZ twins share 100% DNA and DZ 50%

if one twin has it you’d expect the other one would

Question 2

What did Gottesman and Shields 72 do and suggest?

Answer 2

57 Schizoprenic twins between 1948 and 1964.
23 MZ twins and 34 DZ twins
If their twin did not have S followed up for 13 years and found there was 42% likelihood of MZ twins developing S compared to 9% DZ

Question 3

What did Gottesman and Shields 76 do and suggest?

Answer 3

Meta analysis 5 studies

Reported concordance rates of 75% and 91% for twins with severe form of S

Question 4

Why are adoptees used to study genetics on S?

Answer 4

If a biological parent has S, you’d expect the child to develop it regardless of environment

Question 5

What did Tiernari do?

Answer 5

155 adoptees born to S mothers
10% of adoptees with biological S mothers had developed S.
This compared to 1% of adoptees who developed the disorder who did not have S mother

Question 6

Why are family studies used to study genetic S?

Answer 6

Share some genes so you’d expect there to be an increased likelihood

Question 7

What did Kendler do?

Answer 7

Found first degree relatives were 18x more likely to develop the disorder

Question 8

What did Parmas do?

Answer 8

Followed 207 children who had S mothers.

27 year follow up, 16% had been diagnosed with S compared to 2% in a low risk group

Question 9

Evaluation points for Genetic Explanation

Answer 9

Too simplistic
Methodological issues with twins
Methodological issues with adoption studies (contamination effect)
Could be explained by both genes and the environment (Diathesis stress)
Research suggest genetics cannot be only factor
Methodological issues- longitudinal studies

Question 10

What are the methodological issues of twin studies?

Answer 10

May not necessarily be genes may be exposure to environment
Can’t separate environmental and genetic causes
Treated in a similar manner

Question 11

What are the methodological issues of adoption studies?

Answer 11

Contamination effect
May be exposure to biological parent not genetics that caused S
Also, adoption process may play a role- feelings of unwanted and unloved.

Question 12

What is the role of diathesis stress?

Answer 12

Genes may only play a role to make someone more vulnerable to S
Biology loads the gun and environment pulls the trigger