DNA types

The different types of DNA can be classified according to their structure (single-stranded or double-stranded), according to their shape (linear or circular) and according to the way they are packaged (associated with histones or not associated with histones).

• According to its structure:
  • Single-stranded: made up of a single strand. Is found in:
    • Linear form: in parvoviruses.
    • Circular shape: in the ΦX174 virus.
  • Double stranded: made up of two strands.
    • Linear form: in the nucleus of eukaryotic cells and in some viruses, such as bacteriophage T4 and the herpes virus.
    • Circular shape: in prokaryotes, in mitochondria, in chloroplasts and in some viruses such as SV40 and polyoma.

• According to its packaging
  

  • In eukaryotes: associated with histones or protamines (in sperm).

  • In prokaryotes: associated with histone- like proteins, RNA and non-histone proteins.

  • In viruses: it can also be associated with basic proteins of the virus or with histones of the parasitized cell.

  DNA IN DIFFERENT TYPES OF CELL ORGANIZATION
  PROKARYOTES	Double-stranded circular DNA bound to histone-like proteins. Form the nucleoid. It is similar to DNA in mitochondria and chloroplasts.
  EUKARYOTES	Linear, double-stranded, histone linked DNA found within the nucleus with varying degrees of packaging, condensing into chromosomes as the cell is dividing.
  VIRUS	DNA can be linear or circular and single-stranded or double-stranded. Also, some viruses can have RNA as hereditary material.