�y��vlog

In addition to this, no functional differences were seen between psoriasis and non-psoriasis tissue, suggesting that the condition is not linked to a specific somatic mutation in the skin.

To understand the extent of somatic mutation in a human tissue, and the origin of skin cancers, a previous study2 used DNA sequencing of small biopsies of normal epidermis.

However, technical difficulties in detecting the mutations present in a small number of cells, or even in single cells, have hampered research and limited progress in understanding the first steps in cancer development and the impact of somatic mutation on ageing and disease.

Köhler had joined Milstein’s group at the MRC Laboratory of Molecular Biology in Cambridge, UK, as a postdoc, to study the mechanism of somatic mutation that operates in antibody diversification.

He wrote8: “While I was still in medical school, James Cleaver recognized xeroderma pigmentosum as a deficiency in the repair of DNA damage caused by ultraviolet light… I have been a believer in the somatic mutation hypothesis of cancer ever since”.