In eukaryotes, DNA is found in chromosomes in the nucleus. Chromosomes are made of a single molecule of DNA and proteins. Chromosomes are linear, and DNA in them is double stranded. There are many chromosomes in a single nucleus. In prokaryotes, a single DNA molecule which is double stranded forms the chromosome. There are no proteins in the chromosome. In viruses, the genetic material is either DNA or RNA. They may be double stranded or single stranded. It may be circular or linear.
