Epigenetics and Depression

What is DNA made up of?

Genes.

Where do we inherit our genes and chromosomes?

From biological parents — 50% from each parent.

Define epigenetics.

The study of how environmental or physiological factors influence gene expression.

What is genetic expression?

A complex chemical reaction to environmental or physiological changes allowing a gene to function.

When does a gene affect behaviour?

Only when it is expressed (activated).

Define genotype.

The genetic make-up of an individual.

Define phenotype.

Observable characteristics resulting from the interaction between genotype and environment.

Examples of environmental factors affecting gene expression.

Stress, diet, exercise, or other life experiences.

Define concordance rate.

The likelihood that both twins show the same trait or disorder.

How much genetic material do MZ twins share?

100%.

How much genetic material do DZ twins share?

Approximately 50%.

What does high concordance in MZ twins compared to DZ twins suggest?

A genetic component.

Why are MZ concordance rates often below 100%?

Environmental factors also influence gene expression.

Strength of genetic research: reliability.

Twin studies are highly reliable.

Strength: modern methods.

Large-scale studies and genetic mapping help locate genetic variations.

Strength: interactional approach.

Modern research recognises environmental and biological interactions.

Weakness: correlation.

Genetic arguments cannot establish cause-and-effect relationships.

Weakness: population validity.

Samples may not represent the general population.

Weakness: variable isolation.

Impossible to separate genetic and environmental influences.