AP BIOLOGY

Detailed explanation-1: -A histone is a protein that provides structural support for a chromosome. Each chromosome contains a long molecule of DNA, which must fit into the cell nucleus. To do that, the DNA wraps around complexes of histone proteins, giving the chromosome a more compact shape.

Detailed explanation-2: -A nucleosome is a section of DNA that is wrapped around a core of proteins. Inside the nucleus, DNA forms a complex with proteins called chromatin, which allows the DNA to be condensed into a smaller volume.

Detailed explanation-3: -Figure 1: Chromosomes are composed of DNA tightly-wound around histones. Chromosomal DNA is packaged inside microscopic nuclei with the help of histones. These are positively-charged proteins that strongly adhere to negatively-charged DNA and form complexes called nucleosomes.

Detailed explanation-4: -DNA is packaged into chromatin Although DNA is commonly depicted as linear, chromosomal DNA in the nucleus is actually organized into a higher-order structure called chromatin. This packaging is required to fit DNA with a total length of  1 m into a nucleus with a diameter of 10−5 m.

Detailed explanation-5: -The entire DNA strand must fit within the nucleus of a cell, so it must be very tightly packaged to fit. This is accomplished by wrapping the DNA around structural histone proteins, which act as scaffolding for the DNA to be coiled around.