Robin C. Allshire, et al., Human telomeres contain at least three types of G-rich repeat distributed non-randomly, Nucleic Acids Research 17, 1989
Human telomeres do not contain a pure uniform 6 base pair repeat unit but that there are at least three types of repeat.
The distribution of each type of repeat appears to be non-random. Each human telomere has a similar arrangement of these repeats relative to the ends of the chromosome.
Analysing the change in length of the telomeric repeat region between an individuals blood and gremlin DNA reveals that this is due to variable amounts of the TTAGGG repeat and not the other repeat types.
There can only be, on average, a maximum of 8.3kb of TTAGGG like repeats per sperm telomere. In addition approximately 1.2kb of TTGGGG like repeats must be distal to all MnlI and HphI site. The most proximal 1.9kb of each telomeric repeat region is made up of TTGGGG and TGAGGG like repeats, this leaves approximately 3.6kb of the human telomeric repeat region unaccounted for.