Living forever
Every time a normal cell divides, the ends of its chromosomes become shorter. Once they have worn down, the cell dies and is replaced. Cancer cells cheat this system - they retain their long chromosomes by continually adding bits back on. This process allows cancer cells to become immortal. Cells from Henrietta Lacks, an American woman who was diagnosed with cervical cancer in 1951, are still growing. They are used in research laboratories all over the world, many years following her death.
