The nucleic acid is composed of the nucleotide units which from two types of nucleic acid DNA and RNA. DNA serves the genetic material of the all organism except few like viruses where RNA serves as the genetic material.
The Chromosomes are densely packed or condensed form of the DNA which is formed to pass the genetic material to the daughter cells.
Since the DNA is the genetic material which codes for all the information to survive and form a condensed structure called chromosome therefore DNA is sometimes called a molecule of life.
