Question

What are Heterochromatin?

Answer 1

Heterochromatin:

1. Heterochromatin is a kind of DNA that is densely packed or condensed and exists in a variety of forms.
2. These variants fall on a spectrum between constitutive heterochromatin and facultative heterochromatin.
3. Both have a function in gene expression.
4. It was assumed that since it is densely packed, it is inaccessible to polymerases and hence not transcribed; however, according to Volpe et al. (2002) and many other articles since, most of this DNA is transcribed, but it is continually turned over by RNA-induced transcriptional silence (RITS).
5. Recent electron microscopy and OsO4 staining investigations show that the tight packing is not caused by chromatin.