Virtual Genetics Education Centre. The cell cycle, mitosis and meiosis Mitosis DNA, in the form of chromosomes, is divided so that each daughter cell has a complete copy of the genetic material or genome. Meiosis A special form of cell division needed to produce sex cells - for example, sperm and eggs with only one copy of each chromosome. See our detailed explanation below:. Another way to understand the progression of mitosis and meiosis is by thinking about what is happeningto the chromosomes, centrosomes, nuclear membrane and cell plasma membrane at each stage of the process.
Here we show how to do this for mitosis, why not try to recreate this table for meiosis? CC Brian Solis, www. Licensed under the terms of CC-BY Meiosis Venn Diagram. The process of cell division is an intricate dance of molecular machinery that has fascinated researchers for hundreds of years. Advances in microscopy have had a huge impact on the field, from its humble beginnings observing metaphase chromosomes under the light microscope, to more sophisticated technologies today that can ask questions at the molecular level.
However, despite our progress, many questions still remain. While there is only one way for mitosis to go right, there are many ways for it to go wrong. For example, in early mitosis, if there are incorrect contacts between microtubules and chromosomes, chromosomes can become misaligned, which can lead to incorrect segregation of sister chromatids. In late mitosis, how is the cell certain that the time is right to perform cytokinesis?
The chromosome passenger complex CPC is a molecular guardian angel that acts at many stages of mitosis to safeguard the fidelity of the process. At the start of mitosis, the CPC localises all over the chromosomes and acts to modify chromatin, during mitosis it moves to the chromosome centromeres to prevent incorrect microtubule attachments and before cytokinesis the CPC finds its way to the central spindle.
Therefore, a question of ongoing research is how does the CPC elegantly re-localise throughout mitosis to save the day? The chromosomal passenger complex: guiding Aurora-B through mitosis. The Journal of cell biology, 6 , A mitosis-specific and R loop—driven ATR pathway promotes faithful chromosome segregation. Science, , You might remember from above that it is the protein cohesin that holds together sister chromatids in metaphase of mitosis and metaphase II of meiosis.
However, in meiosis I homologous chromosomes must be held together in metaphase I, before these ties are swiftly broken during anaphase I. This feat is performed by a miraculous cellular zipper called the synaptonemal complex SC. This zipper must be strong enough to hold chromosomes together, but it must also be disassembled equally efficiently, otherwise homologous chromosomes will not accurately segregate in anaphase I, leading to a potentially disastrous genetic inequality in the daughter cells.
How exactly this zipper disassembles is a hot topic of research. Polo is not solo in meiosis. Cell Cycle, 17 3 , Zipping and unzipping: protein modifications regulating synaptonemal complex dynamics. Trends in Genetics. The time and duration of meiosis. B, , How long does it take a cell to divide?
Cytometry Part A, 87 5 , Molecular and cellular biology, 4 11 , Restarting life: fertilization and the transition from meiosis to mitosis.
Nature reviews Molecular cell biology, 14 9 , Walther Flemming: pioneer of mitosis research. Nature Reviews Molecular Cell Biology, 2 1 , Nobel Lecture: Cyclin dependent kinases and cell cycle control. Bioscience reports, 22 5 , Then in anaphase II, the chromosomes separate at the centromeres.
The spindle fibers pull the separated chromosomes toward each pole of the cell. Finally, during telophase II, the chromosomes are enclosed in nuclear membranes.
Cytokinesis follows, dividing the cytoplasm of the two cells. At the conclusion of meiosis, there are four haploid daughter cells that go on to develop into either sperm or egg cells. Further Exploration Concept Links for further exploration cell division replication metaphase anaphase telophase linkage chromosome cytokinesis haploid prometaphase principle of segregation principle of independent assortment spindle fibers gamete DNA chromatin nucleus cytoplasm eukaryote prophase recombination principle of segregation Principles of Inheritance.
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