Mendel's Laws (1866)
Gregor Mendel spent 8 years growing 29,000 pea plants, crossing varieties and counting offspring. He identified two laws: the law of segregation (each parent contributes one 'factor' per trait; factors segregate during gamete formation) and the law of independent assortment (factors for different traits are inherited independently). Published in 1866, ignored for 34 years.
Chromosomes and Morgan (1910)
Thomas Hunt Morgan, working with fruit flies, proved that genes are physically located on chromosomes. He discovered sex-linked inheritance and genetic linkage — genes on the same chromosome are inherited together. His group produced the first genetic maps, showing the relative positions of genes on chromosomes.
DNA as the Genetic Material (1944–1953)
Oswald Avery showed in 1944 that DNA, not protein, is the genetic material. Watson and Crick determined DNA's double-helix structure in 1953, using X-ray crystallography data from Rosalind Franklin. The structure immediately suggested how genetic information is copied: the two strands unzip and each serves as template for a new complement.
Recombinant DNA and Biotechnology (1970s)
Restriction enzymes (1970s) could cut DNA at specific sequences; ligase could join pieces. Scientists could now combine DNA from different organisms — recombinant DNA technology. Insulin was produced in bacteria in 1982, the first biotechnology drug. The industry now produces hundreds of drugs, vaccines, and industrial enzymes.
Human Genome Project and CRISPR
The Human Genome Project (1990–2003) sequenced all 3 billion base pairs of human DNA. CRISPR-Cas9 (2012, Jennifer Doudna and Emmanuelle Charpentier) provided a precise, cheap gene-editing tool: a molecular scissors that can cut DNA at any specific sequence. The 2020 Nobel Prize in Chemistry recognized their work. Clinical trials for CRISPR treatments of genetic diseases are underway.
Preguntas Frecuentes
Who discovered DNA?
DNA was discovered as a molecule in 1869 by Friedrich Miescher. Its role as genetic material was proven by Oswald Avery in 1944. Watson and Crick determined the double-helix structure in 1953, using crucial X-ray data from Rosalind Franklin. Watson, Crick, and Wilkins won the 1962 Nobel Prize; Franklin had died in 1958.
What is CRISPR?
CRISPR-Cas9 is a gene editing tool derived from a bacterial immune system. It uses a guide RNA to direct the Cas9 enzyme to cut DNA at a specific sequence, allowing scientists to delete, modify, or insert genes with unprecedented precision. Jennifer Doudna and Emmanuelle Charpentier won the 2020 Nobel Chemistry Prize for its development.
What did the Human Genome Project find?
The Human Genome Project (1990-2003) sequenced all ~3 billion base pairs of human DNA. Key findings: humans have ~20,000-25,000 protein-coding genes (far fewer than expected); only ~1.5% of the genome codes for proteins; humans share ~99.9% of their DNA; and comparison with other species revealed extensive shared evolutionary history.