genetic similarities

Question 1

how do genetic similarities play a role in genetic research

Answer 1

Twin studies are useful to investigate the influence of genetics on behaviour.
Monozygotic twins (MZ) show a higher concordance rate than dizygotic twins
(DZ).
● However, these concordance rates are never 100% because environmental
factors like diet and exercise impact what genes are expressed.

Question 2

STUDY 1

Answer 2

Bailey and Pillard

Question 3

Aim

Answer 3

to determine the concordance rate of homosexuality in twins

Question 4

Procedure

Answer 4

+ male monozygotic, dizygotic and non-related adopted brothers raised together with at least 1 twin or member of a sibling pair, self-identifying as gay were used
+ recruited via gay publications
+ quasi experimental design–>correlational
+sexual orientation of participants was assessed either by asking relatives or if necessary asking the participants
+ they filled out questionnaires to assess childhood gender nonconformity (CGN) : a phenomenon where a prepubescent child doesn’t conform to the gender patterns or identify with the opposite gender.

Question 5

Results

Answer 5

50% mz were both homosexuals
20% dz were homosexual
11% non-related adoptive brothers were homosexuals
9% related non-twin siblings were homosexuals
childhood gender nonconformity was not correlated with homosexuality

Question 6

conclusion

Answer 6

the more closely genetically related the pair is the higher the concordance rate for homosexuality.

Question 7

evaluation

Answer 7

recruitment not inclusive for closeted or unsure people
no actual gene just link
can be influences by sociocultural norms

Question 8

STUDY 2

Answer 8

kendler et al

Question 9

Aim

Answer 9

To investigate the level of heritability of depression in twins.

Question 10

Procedure

Answer 10

42,000 Swedish twins were tested for major depression.
2. Concordance rates were found.

Question 11

results

Answer 11

MZ twins had higher concordance rate than DZ but was less than 100%.
● The heritability of depression was around 38%

Question 12

conclusion

Answer 12

Since the concordance rate and heritability was less than 100%, this indicates
that the environment also plays a role in triggering major depression.

Question 13

evaluation

Answer 13

Telling the twins about the results could have caused a self-fulfilling prophecy
to occur.
● However, not informing the twins about the results is also unethical.
● In this case, it’s difficult to determine whether the twins should have been told
the results or not.