History of genetics

The history of genetics traces how explanations of heredity developed from early theories to the study of genes, chromosomes, and DNA.

Preformationism: The theory that an organism exists in miniature within a reproductive cell and merely grows during development. It opposed the idea that heredity combines contributions from both parents.
Chromosome theory of inheritance: The theory that genes are located on chromosomes, which segregate during cell division. It connected Mendel’s abstract hereditary factors to structures inside cells.
Rosalind Franklin: A British chemist whose X-ray diffraction studies revealed key structural features of DNA. Her diffraction data were central to identifying DNA’s helical structure.
Polymerase chain reaction: A laboratory method that rapidly amplifies selected DNA sequences. PCR made genetic analysis practical with small starting samples.
Modern synthesis (1930s–1940s): A framework that united Mendelian genetics with Darwinian evolution through population genetics. It reconciled inheritance with natural selection and reshaped evolutionary biology.
Blending inheritance: A discredited model in which parental traits mix continuously in offspring. Its apparent incompatibility with persistent variation helped motivate Mendel’s experiments.
Thomas Hunt Morgan: An American geneticist whose fruit-fly research linked genes to chromosomes and revealed genetic linkage. His laboratory supplied experimental evidence for chromosome-based inheritance.
James Watson: An American molecular biologist who co-developed the double-helix model of DNA with Francis Crick. His model helped redirect genetics toward molecular mechanisms.
DNA sequencing: The determination of the nucleotide order in a DNA molecule. Sequencing transformed genetics from studying individual traits to reading entire genomes.
Population genetics: The study of genetic variation and allele frequencies within and between populations. It provided mathematical tools for connecting heredity to evolution.

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