Mitosis is a type of cell division in which a single parent cell divides to form two genetically identical daughter cells. It plays a crucial role in the growth, repair, and maintenance of multicellular organisms.
Based on the behavior of the nuclear envelope during cell division, mitosis is of two main types: Open mitosis and Closed mitosis
Open Mitosis
When mitosis occurs in an open cytoplasmic environment due to the disappearance of the nuclear membrane, the process is called open mitosis.
- Open Mitosis is also known as "free" mitosis.
- It involves the breakdown of the nuclear envelope during the entire process
- It allows spindle fibres to interact with chromosomes in the cytoplasm.
- It is common in higher eukaryotes, including plants and animals.
Features of Open Mitosis
- Breakdown of Nuclear Envelope: The nuclear envelope completely disassembles during late prophase and prometaphase.
- Spindle Formation in Cytoplasm: The spindle fibres form in the cytoplasm and attach directly to the centromeres of chromosomes.
- Reformation of Nuclear Envelope: During telophase, the nuclear envelope reforms around each set of separated chromosomes, forming two daughter nuclei.
- Common in Higher Eukaryotes: Found in various organisms, especially plants and animals.
Closed Mitosis
Closed mitosis is a type of cell division in eukaryotic cells where the nuclear envelope remains intact throughout the process.
- The Closed Mitosis, also known as "enclosed" mitosis.
- It is found in Fungi, protists and some lower eukaryotes.
- The spindle apparatus forms inside the nucleus or is associated with the nuclear envelope.
- The chromosomes align, separate and move to the opposite pole without breaking the nuclear membrane.
Features of Closed Mitosis
- Intact Nuclear Envelope: the nuclear envelope remains intact throughout the entire process of mitosis and does not break down at any stage.
- Spindle Formation inside the Nucleus: The spindle fibres form and function within the nucleus, allowing chromosome movement without exposure to the cytoplasm.
- Continuous Nuclear Structure: The nucleus remains single and intact until cytokinesis, after which two daughter cells are formed.
- Common in Lower Eukaryotes: Found in Fungi, protozoa, and some unicellular eukaryotes.
Below are some of the main differences between Open mitosis and Closed mitosis:
Characteristics | Open Mitosis | Closed Mitosis |
|---|---|---|
Nucleus Status | The nucleus disappears during mitosis | The nucleus remains intact throughout mitosis |
Nuclear Envelope | Nuclear envelope disassembles during the prophase /Prometaphase | The nuclear envelope remains intact |
Common in Organisms | Commonly found in higher organisms | Commonly found in lower organisms |
Chromosome Movement | Chromosomes move freely in the cytoplasm | Chromosomes move within the nucleus |
Spindle Formation | The Spindle fibers are formed in the cytoplasm | The Spindle fibers are formed inside the nucleus |
Cytokinesis | Occurs after mitosis | Occurs after mitosis |
Examples | Plants, Animals, and Mammals | Yeast, Fungi, and some protozoa |
