4 public questions tagged with this topic.
Unlike eukaryotic DNA, prokaryotic DNA is not associated with histone proteins for packaging.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance DNA Structure Double Helix and Packaging - Nucleosome
A prokaryotic cell lacks a well-defined nucleus. Its genomic DNA is generally a single circular chromosome that remains naked because it is not enclosed by a nuclear membrane. Plasmids, when present, occur in addition to the genomic DNA.
Ref: NCERT Class 11 Biology Chapter 8: Cell: The Unit of Life Cytoskeleton Cilia Flagella Centrosome Nucleus and Chromosomes
Bacterial chromosomes possess single origin of replication oriC where DnaA-ATP binds DnaA boxes, unwinds DUE and recruits DnaB helicase with DnaC loader. Replication proceeds bidirectionally toward terminus region defined by Tus-Ter complexes. Because only one origin fires per chromosome per cell cycle, bacterial chromosome is monorepliconic. Some bacteria with secondary chromosomes or megaplasmids may appear multirepliconic but canonical E. coli remains model monoreplicon system. Regulation ensures initiation once per cycle via SeqA sequestration and DnaA inactivation, preventing over-replication and maintaining copy number control.
Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 5: Bacterial Chromosome is Usually Monorepliconic
Prokaryotic chromosomes typically consist of single large DNA molecule occupying nucleoid region without nuclear envelope. Most bacteria including Escherichia coli carry circular, supercoiled chromosome of several megabases organized in loop domains constrained by HU, FIS and H-NS proteins. Circular topology confers replicative advantage with single origin oriC and bidirectional replication terminating at dif site. Exceptions exist such as linear chromosomes in Borrelia, Streptomyces and Agrobacterium, but archetypal pattern remains circular double-stranded DNA often associated with plasmids providing accessory functions under selection pressures.
Ref: Lewin B., Genes XII, Chapter 13: Prokaryotic Chromosomal DNA is Usually Circular, Bacterial Genome
