Nucleoid: Definition, Function & Structure

Nucleoid: Definition, Function & Structure
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  • 0:01 Intro
  • 0:47 What Is the Nucleoid?
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Lesson Transcript
Instructor: John Williams
The nucleoid is the region of a prokaryotic cell that houses the primary DNA. This lesson briefly discusses the nucleoid and its characteristics and how it compares to the nucleus of the eukaryotic cell.

Eukaryotic vs. Prokaryotic Cells

The cell is the smallest unit of life. Cells come in two basic forms: eukaryotic and prokaryotic. Eukaryotic cells are cells that have a 'true' nucleus, or central compartment for DNA, which is genetic material, and other organelles that contain membranes. This nucleus contains a membrane to protect the interior where the DNA is housed. In a sense, the nucleus is the 'control center' of the eukaryotic cell, directing the activities.

Prokaryotes, on the other hand, lack organelles and membrane-bound structures within the cell. This means they also lack a 'true' nucleus, and therefore, the DNA of the cell is not protected by a nuclear membrane. For prokaryotes, DNA will be housed in a region known as the nucleoid.

Prokaryotic Cell

What Is the Nucleoid?

The nucleoid is the region in the prokaryotic cell that contains the main DNA material. As a side note, some DNA will be in other sections of the cell, but the primary material will be in the nucleoid. The nucleoid has an irregular shape compared to the nucleus of eukaryotic cells, which is circular.

DNA in the nucleoid is circular and may have multiple copies at any given time. Additionally, DNA in the nucleoid may be supercoiled, meaning it has twists in the circular shape that makes it more compact. As the cells grow, the DNA in the nucleoid may extend into the cytosol, or cellular fluid.

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