Mitosis in eukaryotes and binary fission in prokaryotes share the similar goal of dividing one cell into two copies that have the same DNA content. They are both orderly processes that consist of certain steps that must happen before subsequent steps can take place. There are major differences between what has to happen, such as degradation and reformation of the nuclear membrane in eukaryotes, but the overall goal is to accurately replicate the DNA content. The duplicated DNA must then be separated into opposite ends of the dividing cell. The two daughter cells must then form new membranes and/or walls where they were formerly joined, so that each cell can be a self-contained entity.
Both eukaryotes and prokaryotes carry their genetic information in the form of DNA. When either undergoes cell division, the DNA must be accurately replicated so that each daughter cell receives the same amount of DNA as was in the parent cell. In eukaryotes, the DNA is replicated during S-phase of the cell cycle, which is part of interphase, or the preparation phase that takes place before mitosis happens. Prokaryotes do not have membrane-bound organelles, which means their DNA is not surrounded by a nuclear membrane -- they do not have a nucleus. However, prokaryotes have a yarn ball of DNA called a nucleoid, which needs to be replicated before the prokaryote undergoes binary fission.
The Great Walls
Cytokinesis is the process of physically separating the two daughters of mitosis or binary fission into completely separate cells. In eukaryotic animals cells, this happens by pinching the membrane between the two daughter cells so that the cells become disconnected. In eukaryotic plant cells, which have cell walls that cannot be pinched, the two separating daughter cells form a new wall between themselves. Plant cell walls are made of cellulose fibers. Fungi are also eukaryotes that have cell walls, made of fibers of chitin, that need to be joined for the formation of a new wall. Lastly, different eukaryotic protists also have different cell walls, made of various molecules including silica, pectin and cellulose, which need to be formed carefully during cytokinesis. Along the same theme in eukaryotes, prokaryotes also have cell walls, but made with peptidoglycan polymers that are unique to them. The last step of binary fission is both to pinch the cell membrane and form a new cell wall, called a septum, which eventually splits the daughter cells into two separate cells.
Eukaryotes differ from prokaryotes in that eukaryotes have membrane-bound organelles such as mitochondria, the endoplasmic reticulum, golgi body and other vesicles. This means that during cell division, a eukaryote must keep track of more things than does the prokaryote. The process of mitosis needs to make sure that the organelles also divide and are evenly distributed between the daughter cells. Organelles divide during the G2-phase of the cell cycle’s interphase, right before the cell enters mitosis.
You Break It, You Make It
One of the membrane-bound organelles of the eukaryote is the nucleus, which holds the DNA in the form of chromosomes. The nuclear membrane must be broken down during prophase, and then reformed after telophase when the two daughter cells split. To better appreciate the complexity of this process, which eukaryotes must deal with during mitosis, it helps to understand that the nuclear membrane is not just a lipid bilayer, but is held together by a protein scaffold on its inner wall. The scaffold is made of proteins called lamins, and serves to give the nucleus its shape and to provide docking sites for chromatin, which is DNA packaged with proteins.
- Molecular Cell Biology: Overview of the Cell Cycle and Its Control
- Cornell University, Department of Microbiology: Binary Fission and other Forms of Reproduction in Bacteria
- PH School: Cytokinesis in Plant Cells
- Todar’s Online Textbook of Bacteriology: Structure and Function of Bacterial Cells
- University of Massachusetts, Department of Microbiology: Exploring structure and function of FtsZ
- Essentials of Cell Biology: Eukaryotic Cells Possess a Nucleus and Membrane-Bound Organelles
- University of Oregon, Department of Biology: Interphase - G1, S and G2
- Scitable: Replication and Distribution of DNA during Mitosis
- The Cell: A Molecular Approach: The Nuclear Envelope and Traffic between the Nucleus and Cytoplasm
- University of New Mexico, Dept. of Biology: Protists
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