Final answer:
The complex of DNA and protein in chromosomes is called chromatin, which is composed of DNA wrapped around histone proteins, forming structures known as nucleosomes.
Step-by-step explanation:
The complex of DNA and protein in chromosomes is called chromatin.
Chromatin is composed of DNA wrapped around histone proteins, forming a DNA-histone complex known as a nucleosome.
During cell division, chromatin condenses into chromosomes, ensuring safe DNA transport to daughter cells. Histones are evolutionary conserved proteins pivotal to this structure, with the chromatin being further packed during the metaphase stage of cell division.
When chromatin is not as tightly packed, it forms regions called euchromatin which contain genes that are actively transcribed, whereas tightly packed regions, called heterochromatin, contain inactive genes.