The nucleoid (meaning nucleus-like) is an irregularly-shaped region within the cell of a prokaryote that contains all or most of the genetic material.[1] In contrast to the nucleus of a eukaryotic cell, it is not surrounded by a nuclear membrane. The genome of prokaryotic organisms generally is a circular, double-stranded piece of DNA, of which multiple copies may exist at any time. The length of a genome widely varies, but generally is at least a few million base pairs.
A genophore is the DNA of a prokaryote. It is commonly referred to as a prokaryotic chromosome. The term "chromosome" is misleading for a genophore because the genophore lacks chromatin.[2] The genophore is compacted through a mechanism known as supercoiling,[3] whereas a chromosome is additionally compacted via chromatin. Nevertheless many prokaryotic organisms employ some specialized proteins (that can be considered as "histone-like" proteins) in order to spatially organize the genetic material so that picturing the nucleoid as an unorganized blob turns out to be quite misleading.