Genetic chaos

Every time a healthy human cell divides, it copies all its genes, which are bundled up into 46 chromosomes. This process has several checkpoints to ensure that each new cell gets a near-perfect copy. But in a cancer cell, these checkpoints are often missing. The result is chaos: parts of chromosomes may be lost, rearranged or copied many times and the genes are more likely to acquire further mutations. Some of these may allow the cell to escape other checking and repair mechanisms.

Chromosomes from a normal cell (above). In a cancer cell (below), parts of chromosomes may be lost, rearranged or duplicated. Sharon Horsley, Jill Brown, Sabrina Tosi, Lyndal Kearney, Institute of Molecular Medicine, Oxford