Heterochromatin term was proposed by Emil Heitz in 1928.
It is present in the genome of eukaryotes.
It is the dark matter of the genome that silences the expression of genes.
Heterochromatin are a tightly packed form of DNA in the nucleus. They are so compactly organized that they are inaccessible to the protein involved in gene expression.
These are of two types – facultative heterochromatin and constitutive heterochromatin.