Branches
The branches differ mainly in scale: a single molecule, a family, a population, a whole genome.
| Branch | What it studies | Typical question |
|---|---|---|
| Classical (transmission) genetics | How traits pass between generations | What is the chance this child inherits the condition? |
| Molecular genetics | The structure and function of genes at the level of DNA and RNA | What does this sequence do, and what switches it on? |
| Population genetics | Allele frequencies and how they change | Why is this variant common here and rare there? |
| Quantitative genetics | Traits shaped by many genes and the environment | How much of the variation in height is inherited? |
| Genomics | Whole genomes: their sequence, structure and comparison | Which of these millions of differences matters? |
| Medical and clinical genetics | Inherited disease: diagnosis, counselling and treatment | Is this variant the cause, or a bystander? |
| Epigenetics | Heritable changes in gene activity without changes in sequence | How does a liver cell stay a liver cell? |
| Evolutionary and developmental genetics | How genes build bodies, and how that has changed | Why do flies and mice share the genes that lay out their body plans? |
The tools that changed the questions
Recombinant DNA (1972–73) made genes something that could be cut and moved. Sanger sequencing (1977) made them readable, and the polymerase chain reaction (conceived in 1983, made public in 1985) made them copyable. The Human Genome Project, declared complete in 2003, turned a gene-by-gene science into one that starts from the whole sequence. CRISPR-Cas9, shown to cut DNA at a chosen site in 2012, made genomes editable; the first therapy based on it was approved in 2023.