The genetic material of microorganisms, be they prokaryotic or eukaryotic, is arranged in an organized fashion. The arrangement in both cases is referred to as a chromosome.

The chromosomes of prokaryotic microorganisms are different from that of eukaryotic microorganisms, such as yeast, in terms of the organization and arrangement of the genetic material. Prokaryotic DNA tends to be more closely packed together, in terms of the stretches that actually code for something, than is the DNA of eukaryotic cells. Also, the shape of the chromosome differs between many prokaryotes and eukaryotes. For example, the deoxyribonucleic acid of yeast (a eukaryotic microorganism) is arranged in a number of linear arms, which are known as chromosomes. In contrast, bacteria (the prototypical prokaryotic microorganism) lack chromosomes. Rather, in many bacteria the DNA is arranged in a circle.

The chromosomal material of viruses is can adopt different structures. Viral nucleic...