Biological Approach - Genetics and Behaviour - Genes

Question 1

Gene

Answer 1

• The biological unit of heredity
• Humans have 46 hromosomes, made up of 23 from the father, and 23 from the mother
• Each chromosome is composed of many individual heredity units called genes
  
  • a gene is a segment of DNA
• They are thought to be responsible for the development of physical and behavioural characteristics

Question 2

Genotype

Answer 2

• The genetic makeup of an individual

Question 3

Phenotype

Answer 3

• The observable characteristics of an individual

Question 4

Allele

Answer 4

• Different verion of the same gene

Question 5

Molecular Genetics

Answer 5

• Method to study the influence of genotype on behaviour
• Studies of molecular genetics are based on using modern technology for gene mapping and identifying the alleles of particular genes in a particular individual
• Gene variants are then correlated with observed behaviour

Question 6

5-HTT Gene

Answer 6

• Serotonin transporter gene
• Comes in 2 different alleles - long and short
• Each individual inherits 2 5-HTT
  
  • some have 2 long
  • some have 2 short
  • some have 1 long 1 short

Question 7

Caspi et al. (2003)

Answer 7

Aim:
- Investigate whether the short allele in the 5HTT gene in combination with stressful life events increases the risk of depression in an individual

Pps:
- 847 New Zealand Caucasian

Procedure:

• Pps were genotypes and divided into 3 groups
  
  • Group 1: 2 short alleles
  • Group 2: 1 short 1 long allele
  • Group 3: 2 long alleles
• Pps were asked to gill in a “stressful life events” questionnaire
  
  • asked them about their frequency of 14 events
    
    • financial
    • emplyment
    • health
    • relationship stressors
  • also assessed for depression
    
    • 17% had MDD

Results:

• Pps who inherited one or more short versions of the allele demonstrated more symptoms of depression and suicidal ideation in response to stressful life events
• The effect was strongest for those with three or more stressful life events
• Simply inheriting the gene was not enough to lead to dperessions, bu the genes’ interaction with stressful life events increased one’s likelihood of developing depression