Each chromosome contains one DNA double helix molecule before replication and once the chromosome is replicated. the number of DNA becomes two as in the case of chromosome monosome.
Chromosomes are the genetic material, the carriers of genes in the human body. Chromosomes are nucleoprotein complexes composed of DNA, histones and RNA, etc. They are carriers of nuclear genes and are highly helical DNA protein fibers.
The basic unit of DNA is nucleotide, including a pentose sugar, a base and a phosphate group, two polynucleotide chains parallel to each other reverse winding constitutes the DNA double helix macromolecule, which is not only the main component of the chromosome, but also the main genetic material.