Question

Which of the following is correct?

a) INTERPHASE DNA is randomly distributed in the nuclear compartment
b) Ribosomal RNA is synthesized and processed outside of the nucleolus
c) DNA binding proteins are Histone based only
d) Chromatin remodeling complexes can not alter accessibility to the DNA
e) There are only two layers of DNA packing in the mitotic chromosome
f) Histones do not have lysine amino acids through which they may acquire modifications (phosphates, methyl groups, and acetyl groups)

Answer 1

During interphase, DNA can exist in condensed forms called heterochromatin and euchromatin. The first level of compaction involves wrapping DNA around histone proteins to form nucleosomes. Histones can undergo modifications that affect gene expression.

Step-by-step explanation:

During interphase, DNA exists in more or less condensed forms called heterochromatin and euchromatin. Heterochromatin contains inactive genes and is tightly packaged with additional chromatin proteins. Euchromatin contains active genes and is more dispersed, allowing easier access to the DNA.

The first level of compaction is the wrapping of DNA around histone proteins to form nucleosomes in a 'beads on a string' structure. Multiple nucleosomes then coil into a 30 nm fiber. Higher-order packing of the 30 nm fiber leads to the formation of metaphase chromosomes seen during mitosis and meiosis.

Histones can undergo modifications such as phosphorylation, methylation, and acetylation, which can affect gene expression. These modifications occur mostly on specific amino acids, including lysine.