Genetic relatedness

Question 1

Define epigenetics

Answer 1

Epigenetics argues that in order for a behaviour to occur, genes must be expressed, as a reaction to environmental or physiological changes.
- environmental factors like stress, exercise, or diet, may result in genetic expression or lack of

Question 2

Define twin study

Answer 2

Any differences between monozygotic twins can be attributed to environmental influence due to 100% genetic similarity

• how genetic a behaviour is
• correlational research that uses concordance rates to estimate the heritability of a behaviour

Question 3

Define family study

Answer 3

Uses principle of genetic relatedness but compares relatives on a broader scale and across generations

Question 4

Kendler et al

Answer 4

Aim: investigate the heritability of depression

• twin study
• 42 000 twins

Procedure:

1. Accessed the Swedish National twin registry
2. ran a statistical analysis

Results:

Concordance rates
Male MZ twins - 31%
Male DZ twins - 11%
Female MZ twins - 44%
Female DZ twins - 16%

Conclusion
Overall depression was concluded to be 38% heritable - depression must be the result of a genetic predisposition or vulnerability, but the environment must be right for the gene to be expressed

Evaluation

• ethical consideration with informed consent
• perhaps not generalisable due to ethnocentricity
  
  • very large sample across time
    
    • maybe more twins at a specific age
• correlates with other research
• whole sample is twins - not representative of general population
• family studies and studies of genetic markers is required to validate
• only taking into account health records, one twins may not be diagnosed
  
  • reporting bias due to stigma,

Question 5

Weissman et al

Answer 5

Aim: to determine the potential genetic nature of Major Depressive Disorder

• longitudinal family study (20 years)
• 161 grandchildren, parents, grandparents
• method triangulation
  
  • interviews
  • diagnoses from clinicians
• IV: grandparents depressed or not depressed

Participants

• original sample of depressed patients selected from an outpatient specialised clinic
• non-depressed participants were selected from same local community

Procedure

1. participants were selected and monitored for 20 years, undergoing 4 interviews during this period
2. clinicians then evaluated the participants (psychologists and/or child psychiatrists)

Results

• Researchers found high rates of psychiatric disorders in grandchildren with 2 generations of MDD, where 59.2% were showing signs of a psychiatric disorder by 12 yrs.
• Children had increased risk of any disorder if depression was observed in both grandparents and the parents compared to children where their parents were not depressed
• severity of a parent’s depression was correlated with an increased rate of a mood disorder in the children

Conclusion
Therefore, there is a genetic correlation between MDD in generations and the rate of mood disorders in children

Evaluation

• longitudinal - ⬆️ reliability
• The association between parental MDD and child diagnosis moderated by grandparental MDD status.
• researcher triangulation - ⬆️ credibility
• no specific genotype studied