Heterochromatin: Constitutive

Abstract Heterochromatin consists of a variety of nontranscribed tandemly repeated and interspersed repetitive deoxyribonucleic acid DNA sequences. The major classes of tandemly repeated DNA are: satellite DNA, composed of very long arrays mainly found in and around centromeres; minisatellite DNA, composed of moderately sized arrays located at or close to telomeres; and microsatellites, defined by short arrays and dispersed throughout the human genome. long interspersed nuclear elements and short interspersed nuclear elements are the two major classes of interspersed repeats, also referred to as transposon‐derived repeats. Rare fragile sites involve large expansions of microsatellites or minisatellites.