Sometimes, when chromosomes shatter from losing their telomeres, they reform into large circular messes.
“Now for the first time, David Thomas from the Garvan Institute in Sydney, Australia, and his colleagues have sequenced these giant chromosomes and reconstructed their evolutionary history.
First a chromosome is catastrophically shattered when it loses the caps on its ends that hold it together – known as telomeres.This is a process called chromothripsis, discovered in 2010.
Natural DNA-repair mechanisms then kick in and put the pieces back together, but in a complete hotchpotch, which usually means the cell would die. But occasionally these chromosomal oddities survive, and without any telomeres, their ends join together in a ring.
The monsters don’t stay circular for ever. ‘At a certain point, the circle stops growing and becomes linear,’ says Tony Papenfuss from Walter and Eliza Hall Institute of Medical Research in Melbourne, Australia. It does that by grabbing telomeres from other chromosomes, which makes it straight and stable again.
But the team found the monster is much more likely to pick up repeats of genes known to be important to cancer. ‘There’s selection going on,’ says Thomas. To test whether those cancer genes help the monster survive, they tried blocking them. When the genes were blocked, the cell died.” – New Scientist