Describe Heterochromatin.
Highly condensed throughout cell cycle
Characteristic feature of centromeres, telomeres, seen at some other (often ill-defined) chromosomal locations
Typically composed of highly repetitive DNA sequences (tandem repeats)
Generally contains very few genes – exhibits little transcription
Genes translocated into heterochromatic sequence (through chromosome breakage and rejoining) are typically transcriptionally inactivated
Every female (2X) somatic cell contains one inactive X chromosome (the “Barr body”) that is heterochromatic and highly condensed