Dougherty (1975) divided cells into two groups based on the structure of the nucleus.
1. Prokaryotic cell: The word Prokaryotic is formed from Greek word pro meaning origin and karyon meaning nucleus. Prokaryotic means original nucleus or pseudonucleus. Cells that do not have a well-formed nucleus are called primitive cells. Adiocytes are small in size and less than 5 micrometers. Its cell wall consists of peptidoglycan. It contains 70S ribosomes. Primary cells do not contain chromosomes. It contains only DNA. Its nucleoid is called nucleoid or xenophore. It is low in histone proteins and non-enveloped. It does not undergo cytoplasmic movement or cyclolysis. However, transcription occurs in the cytoplasm. Protozoa like bacteria, blue green algae (BGA), mycoplasma (PPLO), spirochetes, rickettsia etc.
2. Eukaryotic cell: The word Eukaryotic is formed from the Greek word eu meaning actual and karyon meaning nucleus. Eukaryotic means true nucleus. Cells that have a well-formed nucleus are called true cells. Cysts are large in size and more than 5 micrometers. The actual cell size is 10 times larger than the original cell due to the presence of the nucleus alone. Its cell wall consists of cellulose. It contains 80S ribosomes. Cells contain chromosomes and DNA. Cyclosis occurs in its cytoplasm and transcription in the nucleus. Cell division in normal cells occurs in the process of mitosis and meiosis. Algae, fungi, bryophytes, pteridophytes, gymnosperms and angiosperms, somatic cells, germ cells, muscle cells, nerve cells etc.
A type of cell between protocell and protocell is called mesokaryotic cell. Mesokaryotic cells have a nuclear membrane. Its chromosomes are composed of DNA and acidic proteins. For example – Gymnodinium (Algae), Peridineum (Algae), Noctiluca (Protozoa) etc.
