In prokaryotic organisms, nuclear region is not surrounded by a membrane. This undefined nuclear region is known as

In prokaryotic organisms, such as bacteria and archaea, the cell lacks a well-defined nucleus and a nuclear membrane [1][2]. Instead of the membrane-bound nucleus found in eukaryotes, prokaryotes contain their genetic material in an irregularly shaped, undefined region within the cytoplasm known as the nucleoid [1][3]. This nucleoid typically consists of a single, circular double-stranded DNA molecule that is in direct contact with the cytoplasm [2]. Unlike eukaryotic DNA, which is organized into linear chromosomes within a nuclear envelope, the prokaryotic nucleoid is not isolated from the rest of the cell's internal environment. While nucleic acids refer to the DNA and RNA molecules themselves, and nucleosomes are structural units of eukaryotic chromatin, the term 'nucleoid' specifically describes this distinct, non-membrane-bound nuclear region in prokaryotes [3].

Sources

1. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.5 Why Is Cell Considered to Be a Basic Unit of Life? > p. 24
2. [2] https://www.nature.com/scitable/definition/prokaryote-procariote-18/
3. [3] https://en.wikipedia.org/wiki/Nucleoid