Question

Heterochromatin that is associated with specific chromosomal positions, such as the telomeres and centromeres, and is always densely packed is called:

• A. Methylated heterochromatin
• B. Epigenetic heterochromatin
• C. Constitutive heterochromatin
• D. Facultative heterochromatin

Answer 1

Answer- Constitutive heterochromatin

Heterochromatin is a form of chromatin that is densely packed , as opposed to euchromatin, which is lightly packed and found in the nucleus of eukaryotic cells.Heterochromatin is in such a condensed structure that it does not enable DNA and RNA polymerases to access the DNA, therefore preventing DNA replication and transcription.There are two main types of heterochromatin, constitutive heterochromatin and facultative heterochromatin.These two types can be distinguished based on their features.

constitutive heterochromatin is the stable form of heterochromatin , i.e. it does not loosen up to form euchromatin and contains repeated sequences of DNA called satellite DNA . It can be found in centromeres and telomeres and is usually involved in structural functions.

Facultative heterochromatin , on the other hand is reversible ,i.e. its structure can change depending on the cell cycle and is characterized by another kind of repeated DNA sequences known as LINE sequences.