Genes and Genetic Similarity | International Baccalaureate

Genetic Inheritance

Theory that proposes behaviours can be passed down through genes, and is believed that certain experiences cause genes to be expressed.

5 HTT-Gene

Serotonin Transporter Gene

Plays a role in how serotonin is worked through the brain, a neurotransmitter which regulates mood.

The gene carries two alleles, a short (s) and a long (l) one. Those with one or two copies of the short allele are at higher risk of getting depression, especially when faced with stressful life events.

Twin Studies

If concordance rates are higher in identical twins than fraternal twins, it shows evidence that certain behaviours have a genetic component.

Genetic Similarity of Twins

• Identical/Monozygotic Twins = 100%

• Fraternal/Dizygotic Twins = 50%

Family/Kinship Studies

Researchers study several generations of a family to see if a behaviour repeats itself. It if does, there seems to be a genetic component to a behaviour.

Genetic Similarity for Family

• Grandparent-Parent = 50%

• Parent-Child = 50%

• Grandparent-Child = 25%

Testability for Theory

• Human Research —> Correlational

• Animal Research —> Cause-and-Effect, to what extent can findings be generalized to humans?

Application for Theory

• Research can explain why certain behaviours run in a family and also shows an interaction between envrionment and genetic predisposition influences behaviours to be shown.

• Preventative Health

Caspi (2003)

An association study that shows there’s a correlation between short 5 HTT-genes and a risk for depressio in relation to stress events.

Kendler et al (2006)