Use of kinship/twin studies in the study of inheritance of behavior

Question 1

Concordance rate

Answer 1

The probability that the same trait will be present in both members of a pair of twins

Question 2

Dizygotic Twins

Answer 2

This occurs when two eggs are independently fertilized by two different sperm cells in the uterus wall at the same time. These twins share 50% of the same DNA.

Question 3

Monozygotic Twins

Answer 3

This occurs when a fertilized egg splits in two in the uterus wall. Identical twins share roughly 100% of the same DNA.

Question 4

Kinship Study

Answer 4

Also known as a family study, this study looks at the frequency of a trait within a family in order to calculate the likelihood that the trait may be inherited.

Question 5

Genetic similarity

Answer 5

How genetically alike two individuals are.

Question 6

Basic point of why kinship/twin studies are used in the study of inheritance of behavior

Answer 6

If two people who are more genetically behavior show more similarity in behavior that those who are less genetically similar, this suggest a genetic influence in the inheritance of behavior.

Question 7

Kendler et al (2006)

Answer 7

Aim:
To investigate whether MDD (Major Depressive Disorder) may be inherited.

Sample:
15,493 complete twin pairs listed in the national Swedish Twin Registry

Procedure:
The researchers used a team of trained interviewers to conduct telephone interviews with each participant to assess lifetime major depression. 8056 twins met the criteria for a diagnosis of major depression at some point in their life.

Findings:
Out of the 8056 twins who met the criteria for MDD at some point in their life, there were significantly higher concordance rates for MZ twins compared to DZ twins. For instance, Female MZ twins had a concordance rate of 0.44 while female DZ twins had 0.16. For male twins, MZ had a concordance rate of 0.31, while MZ had 0.11.