"A series a paralogous regions, within the same species, that could be recognized as deriving from a common ancestor region. For example, the regions on chromosomes 4, 5, 8 and 10 on Figure 1."

http://olan.marseille.inserm.fr/Db/paralogy.html

Highly duplicated information is easier to decode and verify. Chromosomes contain both exactly similar sequences, and very similar sequences, at all scales. The draft of the HumanGenome has revealed that >50% of all DNA sequences above X base pairs duplicate.