Epigenetics and Depression

What are chromosomes?

Thin strands of DNA found in the nucleus of cells.

What is DNA made up of?

Genes.

What do genes contain?

A code that produces specific proteins which determine cell type.

Where do we inherit our genes and chromosomes?

From biological parents — 50% from each parent.

Correct order of biological organisation.

Gene → DNA → Chromosome → Nucleus → Cell.

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.

If a person has a gene linked to a behaviour, what must occur for that behaviour to manifest?

The gene must be expressed.

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.

What does family history suggest about depression?

It tends to run in families, indicating a genetic predisposition.

What do genetic mapping and DNA markers identify?

Specific genes potentially linked to depression.

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.

Weakness: unclear mechanisms.

Even when markers are identified, gene-behaviour interactions remain unclear.