DYS marker mutations

[Amastra]

Can anyone say why a marker mutates,?
What would be the trigger,?
Could it be the enviroment - medical makeup of the host - food - or Interaction with other markers, and when is it most likely to occur, during the lifetime of the host or at the birth of any offspring.?

Any thoughts...

[tomcat]

Some think the short tandem repeats, STR's, add or drop a repeat as needed to preserve Y geometry. Whether that is true or not, one would expect changes to occur when Y replicates, which happens often, from puberty to death. Other than that, the only rule-of-thumb is short STR's tend to add a repeat whereas long STR's tends to drop a repeat.