Genetics

Question 1

Define genetic inheritance

Answer 1

• is the process in which genes (segments of DNA) are inherited from parents to offspring.
• Genes are considered to be responsible for the development of behavioural characteristics.
• does not guarantee because environment also play a role in behaviour.
• Individuals that have inherited certain genes may be pre-disposed to or of risk of mental disorders such as depression.

Question 2

What is the genetics and behaviour involved in the Caspi et al
[Name/Location/Function/Behaviour]

Answer 2

5HTT transporter gene
Function/Behaviour: The 5HTT gene codes for a protein that acts a serotonin transporter, specially involved in the re-uptake of serotonin from the synapse. With efficient re-uptake of serotonin in the presynaptic neuron, the concentration of serotonin decreases and the individual experiences low levels of arousal and lack of positive emotion which can lead to depression. The allele length of the 5HTT gene controls how many serotonin transporters are produced.

Question 3

Aim of Caspi

Answer 3

To investigate whether a functional change in the 5HTT gene is linked to a higher or lower risk of depression in an individual.

Question 4

Method of Caspi

Answer 4

The researchers used an opportunity sample from the cohort of participants who are part in the Dunedin longitudinal research study. In total there were 847 participants of 26 y/o. They were split into three groups depending on the length of the alleles on their 5HTT transporter gene.
Group 1: Two short alleles
Group 2: One short one long allele
Group 3: Two long alleles
Data was gathered on:
- stressful life events occurring after the 21th- before 26th birthday
- past year depression was assessed using the diagnostic interview schedule.
- Correlation was tested between stressful life events and depression, between length of the alleles and depression, and an interaction betwen percieved stress and the length of the alleles.

Question 5

Findings of Caspi

Answer 5

Participants with two short alleles reported more symptoms of depression in response to stressful life events.
Moreover child maltreatment was predictive of depression and adulthood only in adults with either one or two short alleles.

Question 6

Conclusion of Caspi

Answer 6

There is a relationship between short alleles and depression and incidences of stress and subsequent depression.

Long alleles seem to protect against suffering depression as a result of stress (give resilience) which identifies individual differences.

Question 7

Aim of McGuffin

Answer 7

to determine the contribution of genes and shared environments in the developments of depression.

Question 8

Method of McGuffin

Answer 8

177 pairs of same-sex co-twins suffering from major depression

• Diagnostic assessments
• detailed interviews
• interviewers were blind as to whether the twin was one of identical (MZ) or non‐identical (DZ) twins
• had no information on the mental health of the other member of the twin pair.
  The probands and their co‐twins were asked about their shared environment: whether they were still in regular contact; for how long they had lived together, and whether they had shared a bedroom and, if so, for how long.
• asked about the degree to which, as children, friends and parents treated them alike.
• Doctors’ reports from the hospital and from family doctors were also investigated.
• Correlations in the presence or absence of depression in the co‐twin were calculated.

Question 9

Conclusion of McGuffin

Answer 9

• There is a strong genetic component to major depressive disorder, and no evidence for it being caused by a shared family environment.

Question 10

Findings of McGuffin

Answer 10

• The concordance rate of major depressive disorder for MZ twins was 46% and for non-identical (DZ) twins was 20%. This shows that there is a heritability factor for major depression.
  
  • Durations of depressive episodes that were less than 13 months were correlated more strongly with depression in the other twin.