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Nucleoid

In a prokaryote, the nucleoid region is the area in the cell where the single circular chromosome is found. It is not a membrane bound nucleus, as in a eukaryotic cell, but rather floats free. Often, other small circular pieces of DNA called plasmids are found in this area, and throughout the rest of the cell.

Because the nucleoid region does not need to divide, it is much easier for a prokaryotic cell to divide and reproduce. Reproduction is exclusively asexual through binary fission, in which the chromosome is duplicated and attached to the cell membrane on either side of the cell. The cell divides in two, and the chromosome detaches to form another nucleoid region in the two daughter cells.

Sometimes DNA can be transferred between cells in parasexual processes like transformation and transduction.

The lack of a nuclear membrane in the nucleoid region is of critical importance for genetic researchers. The circular chromosome and plasmids of a prokaryotic cell are often used to inject DNA segments the researcher wants to duplicate, and the lack of a membrane ensures the researcher that he or she can get to the DNA with minimal danger of damaging the cell.

Web Resources On Nucleoid

Nucleoid associated proteins
Escherichia coli nucleoid

Book Resources On Nucleoid

Mmm1p functions in mitochondrial DNA nucleoid structure at contact sites by Alyson E. Aiken Hobbs
Structural and functional analysis of the IS903 transposase, and, The role of nucleoid host factors in transposition by Bryan Swingle

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