Question

DNA packaging is the way DNA is folded into chromosomes that affects gene expression by:
A. Controlling access to DNA
B. Positioning related genes near each other.
C. Protecting DNA from mutations.
D. Enhancing recombination of genes.

Answer 1

Hint: Histones aid in the packaging of chromosomal DNA inside tiny nuclei. These proteins have positive charges that firmly cling to DNA with negative charges to form structures known as nucleosomes. Eight histone proteins and 1.65 times of DNA make up each nucleosome.

Complete step by step solution:
Cells coil their DNA strands around scaffolding proteins to produce chromatin, a coiled condensed structure that stores DNA inside the nucleus. Further folding of chromatin into higher tiers of structure gives chromosomes their distinctive shape. By blocking transcription proteins from coming into contact with the DNA, DNA packing frequently inhibits the expression of genes.
Cells appear to exploit such higher packing densities to permanently inactivate genes. For the nucleus of every cell to fit within, DNA has to be compactly packed. At the most fundamental level, nucleosomes are made of structures called histone proteins wrapped around DNA. The histones are octameric, amino acid-rich proteins that have been conserved throughout evolution.
It is believed that RNA polymerase and other factors cannot bind to tightly packed DNA. By blocking transcription proteins from coming into contact with the DNA, DNA packing frequently inhibits the expression of genes. Cells appear to exploit such higher packing densities to permanently inactivate genes.
So, option (A) is correct.

Note:
The DNA of a single human cell can wrap around the cell more than 15,000 times. Therefore, DNA packing is essential because it guarantees that the additional DNA can fit into a cell that is much smaller. DNA can either be circular or linear in bacterial organisms.