Question

Constitutive heterochromatin is
A. Condensed chromatin
B. Present in all cells
C. Made of repetitive bases
D. All of the above

Answer 1

Hint: Heterochromatin is the packed form of the DNA or chromosome material that comes under different varieties. It has a chromosomal material of different density than the normal and the genes it consists of are modified or suppressed.

Complete answer:
Heterochromatin is the area of the chromatin which is darkly stained and it is comparatively in condensed form than the normal one.
This is again of two types.
1. Constitutive heterochromatin
> Constitutive heterochromatin contains the DNA called special type which is called satellite DNA and it is present in a repetitive mode and in all types of cells.
> It is stable and it conserves the heterochromatin properties and it is present as repeated bases
> It has a property of polymorphism and it is due to the presence of satellite DNA.
> It is strongly stained by the C band technique.
2. Facultative heterochromatin.
> It is characterized by the presence of Line like repetitive sequences.
> Facultative heterochromatin is stable and it depends on the stage of development
> One example of the facultative heterochromatin is the presence of the Barr body in the somatic female cells.
> As facultative heterochromatin does not contain the satellite cells, so it does not show polymorphism.
> And it is never stained by c band technique.

So as per the above-given explanation about the constitutive heterochromatin, all of the above is the correct option.

Note:
Other than heterochromatin, the chromatin consist of another type called euchromatin, wherein heterochromatin the material is condensed and not undergo transcription, while the chromatin material in euchromatin is loosely condensed and undergoes transcription.