The portion of chromosome material that remains condensed and is transcriptionally inactive during interphase.
Chromatin staining differently and functioning differently than euchromatin which contains most of the genes. In Drosophila salivary preparations, the heterochromatin is mostly in the chromocenter.
Chromosome material that stains most deeply when the cell is not dividing. It is thought not to represent major genes but may be involved in controlling these genes, and also in controlling mitosis and development.
Highly condensed or folded portions of chromosomes during interphase. They stain less distinctly than euchromatin. There is apparently no transcription of the DNA by messenger RNA (mRNA); these portions may be inactive genes.