Prokaryotic cells are characterised by :

Options

A. a distinct nuclear membrane
B. distinct chromosomes
C. absence of chromatin material
D. absence of nuclear membrane

Explanation

### Step-by-Step Text Solution:

1. **Definition of Prokaryotic Cells**: Prokaryotic cells are defined as cells that lack a true nucleus and other membrane-bound organelles. The term "prokaryote" is derived from the Greek words "pro" meaning "before" and "karyon" meaning "nucleus," indicating that these cells are primitive and do not have a defined nucleus.

2. **Absence of Nuclear Membrane**: One of the key characteristics of prokaryotic cells is the absence of a nuclear membrane. This means that the genetic material (DNA) is not enclosed within a membrane-bound nucleus but is instead located in a region of the cell called the nucleoid.

3. **Free-Floating DNA**: In prokaryotic cells, the DNA is typically circular and free-floating within the cytoplasm. This contrasts with eukaryotic cells, where DNA is linear and contained within a membrane-bound nucleus.

4. **Chromatin Material**: While prokaryotic cells do contain DNA, they do not have chromatin in the same way that eukaryotic cells do. Chromatin is a complex of DNA and protein found in eukaryotic cells that condenses to form chromosomes during cell division. Prokaryotic cells have distinct chromosomes, but they lack the structured chromatin organization.

5. **Comparison with Eukaryotic Cells**: In contrast to prokaryotic cells, eukaryotic cells have a well-defined nucleus that is surrounded by a double membrane (nuclear envelope). Eukaryotic cells also have various membrane-bound organelles, which are absent in prokaryotic cells.

### Summary of Characteristics:
- Prokaryotic cells lack a nuclear membrane.
- DNA is free-floating in the cytoplasm.
- They have distinct chromosomes but lack chromatin structure.
- They are simpler and more primitive compared to eukaryotic cells.