Natural selection is the process where organisms that are best suited to their environment survive and pass on their genetic traits in increasing number to successive generations. At the same time, organisms that are less adapted fail to survive or multiply at a lower rate, and tend to be eliminated from the ecosystem.
Answer:
The two main types of DNA organization present in chromosomes are the extended DNI and the condensed DNI
Explanation:
In eukaryotes, the complete chromosome is composed of only one lineal and extremely long DNA molecule. DNA is intimately associated with two types of proteins: <u><em>histones</em></u>, which are structural proteins, and <em>non-histone</em> proteins that mediate different functions of DNA.
DNA associated with histones is called <u><em>chromatin</em></u>. Histones are responsible for packaging DNA molecule, and the fundamental unit of packaging is known as a <em><u>nucleosome</u></em>. As chromatin must be condensed, nucleosomes generate regular structures between themselves forming a <em><u>chromatinic fiber</u></em>, in which DNA is very condensed. A superior level of condensation is the structural <em><u>ringlet-shaped domain</u></em>. At this level, a chromatinic fiber is folded and a protein is responsible for keeping joined the two regions of DNA that form the ringlet. The next condensation level is the rolling of the ringlet-shaped domain composing the <u><em>chromosome</em></u>. The typical chromosome in the metaphase is formed by <u><em>two chromatids</em></u> joined by a centromere. Each chromatid is composed of a sequence of chromatin ringlets domains. In the interphase, <em>before cellular division</em>, chromatin is in a diffuse, lax, uncondensed state, known as extended DNA. When <em>cellular division</em> is about to happen, chromatin begins to condensate. At the beginning of the <em>prophase</em>, DNA is condensed in a well-defined chromosome formed by two sisters chromatids.
