Afatal central nervous system disorder caused by a copy number variation in which more than 35 repetitions of a particular set of three base pairs are present is

The disorder is Huntington Disease.

Huntington disease is an inherited disorder that results in death of nervous cells in the brain manifested by problems with mental abilities. Symptoms of this disorder vary among the people, but patients’ physical abilities gradually worsen. At same point person can’t talk and dementia occurs.  

nucleus

would be most reasonable answer tbh

answer///multiple alleles;