Question

Centromeres are considered to be: O Heterochromatin O Euchromatin ORNA Unpaired nucleosides 0 Unpaired nucleotides

Answer 1

Ans) Correct option is Heterochromatin. Centromeres are considered to be Heterochromatin. When stains are applied, it gets darkly stained. Heterochromatin is a tightly packed chromatin structure which blocks the access of RNA polymerase and thus pervents transcription. Histone methyltransferases can add methyl groups (positively charged) to the lysine residues and thus the positively charged methyl groups and negatively charged phosphate groups on DNA result in tight interactions thereby leading to tight structure of heterochromatin.

Euchromatin is the result of the acetyl groups on the lysine residues by the enzyme Histone acetyltransferases.Acetyl groups are negatively charged and thus weak interactions between negatively charged histones and negatively charged phosphate groups of DNA result in repulsion or loose interaction and thus open chromatin structure.Now,RNA polymerase can easily bind to the promoter and start transcription.

Centromeres are not RNA. It is the region of DNA .It plays a role in equal chromosome segregation. Kinetochores attach to the centromeres.

Unpaired nucleosides and unpaired nucleotides are also incorrect.