Generalized structure of Archaeal genome

A typical Archaeal genome is very similar to that of a Bacterial one in Table 2. Generally the chromosome is single and circular of a similar size to the Bacteria and may be complemented through the presence of plasmids. The main differences are in the fine structure of the arrangement of genes and the proteins which associate with the genomic DNA.

Although the Archaea have operons and tend to exhibit clustering of genes according to function the arrangement of the genes has elements in common with both the eukaryotes.

                                                 Table 2.  Chromosomal structures  of Archaeal genomes

and the  Bacteria. An Archaeal operon may contain genes which have close relatives in both the other kingdoms and rarely the genes themselves may be made up of domains which may have origins in different kingdoms. However, about a third of the genes in any archaeon are unique to this kingdom.

The replication origin of the Archaeal genome has several features in common with the eukaryotes and this similarity in the gross chromosomal features is apparent by the use of histone-like proteins to stabilize the chromosomal tertiary structure.