The number of monomers that comprise a HOR differs between chromosomes,
conferring chromosome specificity. For example, DXZ1 (HSAX) is defined by a 12
monomer (12-mer) HOR (2kb), while D7Z1 (HSA7) is defined by a 6-mer (1kb) HOR.
Within the population and even between homologs of the same individual, the
total array size (i.e. the number of times a HOR is repeated) is different. The
reported sizes of DXZ1 on single HSAX chromosomes range from 1.3Mb (650 copies
of DXZ1 HOR) to 4.2Mb (2100 copies). Likewise, total array size of D7Z1 ranges
from 1.5 – 3.8Mb, such that in a given individual, D7Z1 on one HSA7
homolog may be 1.8Mb and 3.5Mb on the other homolog.