Researched
Epigenetics
Chemical marks on DNA and its packaging switch genes on and off and are copied when cells divide; Holliday's and Riggs's 1975 proposals launched the field.
Open in the interactive tree →C. H. Waddington coined the word 'epigenetics' in 1942 for the way one fertilised egg's genes produce many kinds of cell. In 1975 Robin Holliday with John Pugh, and independently Arthur Riggs, proposed that methyl marks on DNA could be copied at cell division and so silence genes for good, for instance one of the two X chromosomes in each female cell. Later work linked such marks to cancer, development and ageing: in 2013 Steve Horvath's 'epigenetic clock' estimated a person's age from methylation at 353 sites with a median error of 3.6 years.
Prerequisites
- Structure of DNA1953Methyl marks are chemical tags on the DNA letters themselves.
- Gene Regulation (Operon)1961Genes can be switched on and off; epigenetics asks how that setting is remembered.
Unlocks
- Induced Pluripotent Stem Cells2006Reprogramming factors reset a cell's epigenetic identity back to a stem cell.
- Controlling AgingopenEpigenetic clocks, from 2013, are the main yardstick for biological age.