the genetic explanation support - twin studies

Question 1

in twin studies, what do researchers compare?

Answer 1

researchers compare monozygotic and dizygotic twins.

Question 2

how much dna do monozygotic twins share?

Answer 2

monozygotic twins share all of their dna

Question 3

how much dna do dizygotic twins share?

Answer 3

dizygotic twins share 50% off their dna

Question 4

what is a concordance rate?

Answer 4

the percentage of twins that both share the same trait, given that at least one twin has the trait

Question 5

in twin studies, what do researchers calculate?

Answer 5

for both types of twins, researchers calculate a concordance rate.

Question 6

in twin studies, what do researchers do with the concordance rates they calculate?

Answer 6

the researchers look at the difference between the concordance rate for monozygotic twins and the concordance rate for dizygotic twins.

Question 7

what does a big concordance rate show?

Answer 7

that genetics has a big influence on the trait compared to other factors

Question 8

in the 1960s, what did gottesman and shields conduct and what did they measure?

Answer 8

gottesman and shields conducted a twin study and measured concordance rates for schizophrenia in monozygotic twins and dizygotic twins.

Question 9

what did gottesman and shields find and what do their findings mean?

Answer 9

they found a concordance rate of 74% for monozygotic twins meaning that in 74% of cases where 1 twin had schizophrenia, the other twin also had schizophrenia.

Question 10

since the concordance rate for monozygotic twins wasn’t 100%, what can we say about schizophrenia?

Answer 10

we can say that schizophrenia is not just caused by genetics. schizophrenia development is also influenced by the environment.

Question 11

limitation of twin studies - over exaggeration

Answer 11

• one assumption that twin studies makes is that the environment will have the same impact on phenotype for monozygotic and dizygotic twins.
• one problem with this is that because they are identical, people often treat monozygotic twins as if they are the same person. this doesn’t happen with dizygotic twins. so, as well as having more similar genetics, monozygotic twins might have a more similar environment than dizygotic twins.
• this means that differences in concordance rates between monozygotic and dizygotic twins might be caused by environmental factors as well as genetics, meaning that twin studies might over exaggerate the importance of genetics.