Genetics and Behavior - Biological Approach

Question 1

Human Genome Project

Answer 1

Initiated in 1990, world-wide initiative
Goal was to map & sequence the human genome
Completed in 2004
However, exact role of specific genes in many behaviors is still unknown

Question 2

What are teh 2 types of twins?

Answer 2

Monozygotic (MZ)
Dizygotic (DZ)

Question 3

Monozygotic

Answer 3

genetically identical, formed from one fertilized egg that splits into two (identical twins)

Question 4

dizygotic

Answer 4

develop from two diff. fertilized eggs (fraternal twins)

Question 5

concordance rate

Answer 5

probability that same trait will be present in both twins
High CR for MZ compared to DZ: genetic component to the behavior
High CR for both: environmental factors play a large role in observed behavior

Question 6

kinship studies

Answer 6

(family studies) are used to study behavior or psychological disorders which “run in the family”.

Question 7

basic characteristics of kinship studies

Answer 7

Measure the frequency of behavior across generations
Measure the frequency of a behavior within a generation
Often longitudinal
Case-control studies
Retrospective
Define two groups at start
With behavior/disorder
Without behavior/disorder
Assess statistically significant difference in rates of exposure to defined risk factors
E.g. potential genetic inheritance

Question 8

Weismann et al (2005)

Answer 8

KINSHIP STUIDES –> longitudinal family study for depression
AIM: Study the potential genetic nature of Major Depressive Disorder over 3 generations
PROCEDURE:
Sample of 161 grandchildren and their parents and grandparents
Took place over a twenty year period, looking at families at high and low risk for depression
The original sample of depressed patients (now, the grandparents) was selected from an outpatient clinic with a specialization in the treatment of mood disorders.
The non-depressed participants were selected from the same local community. (environment but less able to generalize)
The original sample of parents and children were interviewed four times during this period.
The children are now adults and have children of their own - allowing for study of the third generation.
Data was collected from clinicians, blind to past diagnosis of depression or to data collected in previous interviews.
In order to establish credibility, researcher triangulation (reliability) was used. Children were evaluated by two experienced clinicians - with one being a child psychiatrist and the other a psychologist.
FINDINGS:
The inter-rater reliability of their diagnoses were 0.82 for MDD, 0.65 for anxiety disorders and 0.94 for alcohol dependency (more quantifiable).
High rates of psychiatric disorders in the grandchildren with two generations of major depression. By 12-years-old, 59.2% of the grandchildren were already showing signs of a psychiatric disorder - most commonly anxiety disorders.
Children had an increased risk of any disorder if depression was observed in both the grandparents and the parents, compared to children where their parents were not depressed. In addition, the severity of a parent’s depression was correlated with an increased rate of a mood disorder in the children.
On the other hand, if a parent was depressed but there was no history of depression in the grandparents, there was no significant effect of parental depression on the grandchildren. (one parent has depression)

Association between parental MDD and child diagnosis is moderated by grandparental MDD status
· Rates of psychopathology are highest in grandchildren of parents and grandparents with a moderately to severely impairing depression
Anxiety disorders are the early sign of psychopathology in the young grandchildren

Question 9

evolutionary osychology

Answer 9

Theory of Evolution proposed by DARWIN (1859) suggests organisms are driven by their need to survive & reproduce
Various human behaviors, including mating behaviors, exhibit characteristics supporting the Theory of Evolution

Question 10

what does MHC stand for?

Answer 10

Major histocompatibility complex

Question 11

what does the MHC gene do?

Answer 11

genes which influence one’s immune system - offspring with diverse MHC genes from parents have a strong immune system & better chances of survival

Question 12

wedekine (1995)

Answer 12

AIM: Investigate influence of MHC genes on mate selection in females
PROCEDURE:
Quasi-experimental study, 49 females and 44 males
Female P. asked to report if using oral contraceptives, given nose spray to ensure nasal health, given a book to sensitize smell perception
Male P. asked to wear shirt for two nights in a row, keep the shirt in a plastic bag between nights, given scentless soap & detergent to ensure natural smell, asked not to partake in activities which may alter their scent, i.e. smoke, drink alcohol, engage in sexual activities etc.
When Female P. in second week after menstruation (when most sensitive to odor) P. were asked to rate odor of 7 shirts on intensity, sexiness and pleasantness
3 male P. with similar MHC genes, 3 with dissimilar MHC genes and 1 (unworn) control shirt
Shirts placed in a cardboard box → double blind study
FINDINGS:
Female P. not on oral contraceptives rated dissimilar MHC higher on pleasantness, vice versa for P. on oral contraceptives
Odors of MHC-dissimilar men reminded females of current/former mates
→ MHC diversity seems to influence mate selection supporting ToE (inc. survival)
As oral contraceptives imitate steroids naturally released during pregnancy, P. may prefer partners who can help them take care of the children