Telomere

Lengths of non-coding, repetitive DNA* sequence present at the ends of linear chromosome*s. These stretches of non-coding sequence help prevent loss of genetic information during replication. 

The DNA polymerase*s responsible for replication need a short priming sequence. The need for a priming sequence prevents the enzyme from starting replication at the extreme 5’ end of linear DNA. The inability to replicate the extreme 5’ linear chromosomes causes the chromosome to get a little shorter during each round of replication. The presence of the telomeric sequence means that short lengths of non-coding, repetitive sequence are lost rather than functional stretches of DNA.