Twin and Adoption Studies

Question 1

What is a Twin Study

Answer 1

Twins are compared on a specific trait to see how similar they are.

Question 2

What is an Adoption Study

Answer 2

Investigates the relationships among genetic and environmental factors in the development of behaviour, comparing it to bio parents.

Question 3

Twin Study Advantages

Answer 3

• Researchers can investigate influence of genes.
• Info for twin studies taken from registries so large samples.

Question 4

Disadvantages of Twin Studies

Answer 4

• May overestimate genetic influence. MZ have more similar environment that DZ. Some similarity could be due to environment.
• Provide indication that behaviour has genetic origin, but cannot identify specific genes.

Question 5

Adv of Adoption Studies

Answer 5

• Show that twin studies overestimate genetic factors.

Question 6

Dis of Adoption Studies

Answer 6

• May be adopted into families similar to biological families, increasing environmental influence.
• People adopting are often unusual, reducing representativeness.

Question 7

Twin: Gottesman and Shields

Answer 7

Investigated genetic basis of SZ.

Searched through records of 45,000 psychiatric patients at a hospital, finding 57 pairs of twins where 1 had SZ. Opp sample.

To establish concordance they contacted co-twins. Zygosity was determined by looking at blood type.

Analysis of this data suggested that if 1 MZ twin had SZ, the co-twin was 42x more likely to have SZ; DZ was 9x.

Question 8

Adoption: Tienari

Answer 8

Conducted Adoptive Family Study looking at SZ.

Found that the lifetime SZ risk for adoptive children of bio mothers who had SZ was 9.4% and 1.2% for unaffected bio parents.

Diff suggests genetic influences have an important role in SZ.