Mitosis and Cell Division

Prokaryotic Cell Division

Cell division in prokaryotes is simpler than in eukaryotes because prokaryotes lack a nucleus and usually have a single, circular chromosome.

Single-celled prokaryotes undergo cell division through a process distinct from that of eukaryotes, or organisms with membrane-bound organelles and chromosomes within a distinct nucleus, primarily because of their lack of a nucleus. Because prokaryotes are unicellular organisms, cell division is asexual reproduction (reproduction that does not involve fusion of gametes, producing offspring genetically identical to the parent). Thus, when a prokaryotic cell divides, each new cell is a completely new organism. Binary fission is the process by which prokaryotic cells divide. It is a type of asexual reproduction. Binary fission is less complex than cell division in eukaryotic cells because there is no need to sort and separate multiple chromosomes.

Binary fission starts when the cell's single circular chromosome begins to replicate. DNA in prokaryotic cells does not form sister chromatids as in eukaryotic cell division. The origin of replication is the place on a chromosome where DNA replication begins. Once a new strand of DNA has begun to form, two origins exist: the origin on the original strand and the origin on the new strand. As DNA replication continues, the origin on the new strand moves to the opposite end of the cell from the origin on the original strand, and the cell elongates. When DNA replication is complete, each chromosome coils toward its origin, segregating the DNA in opposite ends of the elongated cell. The cell pinches off between the coils of DNA, and cytokinesis occurs, separating the cells. The daughter cells are identical, separate organisms.

Reproduction in Prokaryotes

Prokaryotes reproduce asexually through binary fission, the simple division of one cell into two. Prokaryotic DNA is copied starting at the origin of replication site and moves toward the opposite end. When DNA replication is complete, the cell pinches in on itself and separates into two new cells.