twin studies

Question 1

what is a twin study?

Answer 1

a study where a trait/behaviour is compared between twins to see how similar they are

measured by concordance rate

Question 2

what % of DNA do MZ twins share?

Answer 2

100

Question 3

what % of DNA do DZ twins share?

Answer 3

50

Question 4

what is concordance rate?

Answer 4

the degree to which two people are similar on a particular trait/behaviour e.g.
- Aggression
- Schizophrenia
- Addiction

Question 5

what does concordance rate in twins suggest

Answer 5

if a trait/behaviour is entirely genetic, then MZ twins would show 100% concordance.

If a trait/behaviour is influenced more by genes than environment, then we would expect MZ twins to show a higher concordance rate than DZ twins

Question 6

what are strengths of twin studies?

Answer 6

• Allow researchers to measure the influence of genes because each set of twins share an environment, so the only difference between MZ & DZ twins is genetics (MZ 100%, DZ 50%). Therefore the influence of nature vs nurture can be measured.
• Samples usually large because data is taken from twin databases which contain info on many variables (mental health, addiction etc.). Therefore samples can be representative due to being large.

Question 7

what are weaknesses of twin studies?

Answer 7

• Twin studies assume twins grow up in the same environment, but this is wrong because there are small differences between even identical twins. Eg. one twin may be sportier than the other. These differences mean there are actually TWO environmental influences: shared and nonshared.
• Twins studies can’t identify the specific genes involved just a broad indication of whether a behaviour is genetic or environmental. Therefore they are a good starting point but studies which use more scientific methods are need to identify individual genes.