Question

What is constitutive heterochromatin and facultative heterochromatin?

Answer 1

Chromatin is a genetic substance or macromolecule made up of DNA, RNA, and related proteins that make up chromosomes in a eukaryotic cell's nucleus.
When viewed under a light microscope in its extended mode, the structure of chromatin, or nucleosomes, mimics the arrangement of string on beads. Each nucleosome is made up of DNA that is wrapped in eight proteins known as histones. As a result, the presence of histone proteins aids in the maintenance of chromatin structure.

Complete answer:
The telomere regions and regions close to the centromere, as well as some internal segments, contain constitutive heterochromatin. Constitutive heterochromatin is thought to play a role in maintaining total nucleus shape, binding chromatin to the karyolemma, participating in chromosomal recognition during meiosis, and establishing gene spacing.
Information is stored in the facultative heterochromatin. It is a type of chromatin that contains genes and can be converted to euchromatin. A sex chromatin body, found in the cells of species with homogametic sex, is an example of facultative chromatin. In addition, facultative chromatin is formed during cell differentiation processes and serves as a method for turning off the activity of numerous genes that aren't required for the cell's specialisation.
Constitutive heterochromatin is persistent, and the same region of constitutive heterochromatin can be found in all cell types of a species. Facultative chromatin is reversible and does not exist in all of a species' cell types.

Note:

Constitutive heterochromatin	Facultative heterochromatin
The term "constitutive heterochromatin" refers to the DNA sections of the chromosome that remain constant throughout the cell cycle.	Facultative heterochromatin refers to DNA areas where genes have been silenced by changes. As a result, they are selectively triggered in specific circumstances and are not found throughout the cell.
Constitutive heterochromatin includes satellite, minisatellite, and microsatellite sequences.	A form of facultative heterochromatin is made up of long interspersed nuclear components.
The genes cannot be expressed by constitutive heterochromatin.	It is possible to express facultative heterochromatin.