Biological

• What are the assumptions of the Biological Approach?

  Genetic determinism, biological basis of behavior, and the influence of evolution.
• What is the biological Approach?

  explanation of our behaviours mainly in terms of biological factors
• How long has the biological study of the brain and behaviour been going on?


  In parallel with the history of experimental psychology
• Understanding Genetics

  The body is made up of cells and each cell contains 23 pairs of chromosomes
• What does DNA stand for?

  Deoxyribonucleic acid
• What is DNA?

  • the substance that chromosomes are made of
  • a chain of two or more nucleotides joined together
• each cell in your body has the exact same DNA
• What is a gene?

  A gene is a segment of DNA that contains the production of one specific protein.

  • control our physical traits
• Animals of the same species broadly have the same set of genes, and different species have different sets of genes.
• What do we call different versions of a gene?

  Alleles
• if there is different versions of a gene (alleles) we say there is genetic variation in that characteristic e.g. hair colour.
• what are sex cells?

  • either a sperm or egg
  • have 23 chromosomes
• What occurs in reproduction?

  Where a males sex cell (sperm) meets a women's sex cell (eggs) to form a new cell that has 46 chromosomes
• what is genetic inheritance?

  when traits are passed down from parent to child
• what is a genotype?

  A description of all of the genes and alleles in a body
• what is a phenotype?

  The observable characteristics or behaviours of a person (physical traits)
• Genotype + environment = phenotype
• What do we call Environmental factors?

  things in the environment can affect our physical traits e.g. sun
• behaviours and psychological traits are partly inherited
• To sum up, the biological approach studies the extent to which behaviours are determined by genetics and genes determine behaviour by affecting processes inside the brain.
• Environmental factors have a bigger impact on behaviour than they do on physical traits
• What are the two types of twin?

  MZ / Mono-zygotic (same genotypes, 100%)

  DZ / Di-zygotic (different genotypes, 50%)
• What type of twins are Monozygotic?

  identical twins
• What type of twins are dizygotic?

  un-identical twins
• Monozygotic twins come from one Zygote, which splits into two identical zygotes, whereas dizygotic twins come from two different zygotes.
• Both monozygotic and dizygotic twins have some shared and some non-shared environments
• The concordance rate is how often we see a trait or disorder within a group of people who share genes compared with those who do not share genes.
• Concordance rates for MZ twins tend to be higher than for DZ twins because they share more genetic material.
• Assumptions

  • Both MZ and DZ have a similar amount of shared environment
  • Shared environment has a similar impact on phenotype
• What is a shared environment?

  the environment that a pair of twins share in common.
• what is a non-shared environment?

  the environment that a pair of twins don't share in common.
• what do we say for twins that have the same phenotype?

  concordant
• In twin study's, we don't include sets of twins where neither twin has the trait we're studying.
• what is the concordance rate?

  The percentage of twins who share a characteristic, given that at least one twin has the characteristic.
• Genetic variation contributes to a trait if....

  the concordance rate for monozygotic twins is bigger that the concordance rate for dizogotic twins
• The bigger the difference in concordance rates between monozygotic and dizygotic twins, the more influence genetic variation has on the trait.
• In 1996, McGuffin performed a twin study on the presence of depression in twins
• McGuffin found that if one monozygotic twin had major depression, there was a 46% chance the other twin had depression too. They had a concordance rate of 46%.
• For Dizygotic twins, McGuffin found that if one twin had major depression, there was a 20% chance that the other twin did too, having a concordance rate of 20%
• McGuffin could conclude genetic variation does contribute to depression because the concordance rate was bigger for monozygotic (46%) than dizygotic (20%) twins.