An Australian study of 14,000 twin pairs sought to determine if there was a genetic basis for homosexuality. They focused on male identical twins. The researchers found that of the identical twin pairs where one twin was homosexual, 38% of the time the other twin was also homosexual. This suggests there may be a genetic influence for sexual orientation. However, the conclusion has limitations since other environmental factors could also influence sexual orientation.

1. Extra Credit Exam Style Question
An Australian study of
14,000 sets of twins was
carried out to see if there
was any evidence for a
genetic basis for
homosexuality. They focused
on male, identical twins. Of
the study subjects that were
homosexual 38% had a twin
that was also homosexual.
a. Identify how identical twins can arise
................................................................................................................................................
................................................................................................................................................
2 marks
b. Explain why the researchers were interested in identical twins.
................................................................................................................................................
................................................................................................................................................
2 marks
c. Suggest a hypothesis for this investigation
................................................................................................................................................
1 mark
d. Suggest a conclusion for this investigation
................................................................................................................................................
1 mark
e. Suggest why such a conclusion may not be seen as valid
................................................................................................................................................
1 mark

2. Extra Credit Exam Style Question
An Australian study of
14,000 sets of twins was
carried out to see if there
was any evidence for a
genetic basis for
h o m o s e x u a l i t y. T h e y
focused on male, identical
twins. Of the study subjects
that were homosexual 38%
had a twin that was also
homosexual.
a. Identify how identical twins can arise
................................................................................................................................................
................................................................................................................................................
2 marks
b. Explain why the researchers were interested in identical twins.
................................................................................................................................................
................................................................................................................................................
2 marks
c. Suggest a hypothesis for this investigation
................................................................................................................................................
1 mark
d. Suggest a conclusion for this investigation
................................................................................................................................................
1 mark
e. Suggest why such a conclusion may not be seen as valid
................................................................................................................................................
1 mark