The Cell Cycle, Mitosis and Meiosis — University of Leicester
Cytokinesis usually begins just as mitosis is ending, with a little overlap. Because of this, plant cells divide in two by building a new structure down the middle. Cells divide and reproduce in two ways: mitosis and meiosis. Mitosis is a process of cell division that results in two genetically identical daughter cells. A nuclear division (mitosis) followed by a cell division (cytokinesis). chromatids (or sister chromatids) held together by a structure known as the centromere.
The Cell Cycle, Mitosis and Meiosis
Even in animals, cytokinesis and mitosis may occur independently, for instance during certain stages of fruit fly embryonic development. Errors in mitosis can either kill a cell through apoptosis or cause mutations that may lead to cancer.Interphase - Cells - MCAT - Khan Academy
Cytokinesis is technically not even a phase of mitosis, but rather a separate process, necessary for completing cell division. In animal cells, a cleavage furrow pinch containing a contractile ring develops where the metaphase plate used to be, pinching off the separated nuclei. In both animal and plant cells, cell division is also driven by vesicles derived from the Golgi apparatus, which move along microtubules to the middle of the cell.
In plants this structure coalesces into a cell plate at the center of the phragmoplast and develops into a cell wall, separating the two nuclei.
The phragmoplast is a microtubule structure typical for higher plants, whereas some green algae use a phycoplast microtubule array during cytokinesis. The prefix inter- means between, reflecting that interphase takes place between one mitotic M phase and the next.
Image of the cell cycle. Interphase is composed of G1 phase cell growthfollowed by S phase DNA synthesisfollowed by G2 phase cell growth.
At the end of interphase comes the mitotic phase, which is made up of mitosis and cytokinesis and leads to the formation of two daughter cells. Mitosis precedes cytokinesis, though the two processes typically overlap somewhat. M phase During the mitotic M phase, the cell divides its copied DNA and cytoplasm to make two new cells.
M phase involves two distinct division-related processes: In mitosis, the nuclear DNA of the cell condenses into visible chromosomes and is pulled apart by the mitotic spindle, a specialized structure made out of microtubules.
Phases of the cell cycle (article) | Khan Academy
In plants a cell plate forms along the line of the metaphase plate; in animals there is a constriction of the cytoplasm. The cell then enters interphase - the interval between mitotic divisions. Meiosis Meiosis is the form of eukaryotic cell division that produces haploid sex cells or gametes which contain a single copy of each chromosome from diploid cells which contain two copies of each chromosome.
As in mitosis, meiosis is preceded by a process of DNA replication that converts each chromosome into two sister chromatids. Meiosis I Meiosis I separates the pairs of homologous chromosomes. In Meiosis I a special cell division reduces the cell from diploid to haploid. Prophase I is divided into five phases: Prometaphase I Spindle apparatus formed, and chromosomes attached to spindle fibres by kinetochores.
Metaphase I Homologous pairs of chromosomes bivalents arranged as a double row along the metaphase plate. The arrangement of the paired chromosomes with respect to the poles of the spindle apparatus is random along the metaphase plate. This is a source of genetic variation through random assortment, as the paternal and maternal chromosomes in a homologous pair are similar but not identical.
Cell division: mitosis and meiosis
The number of possible arrangements is 2n, where n is the number of chromosomes in a haploid set. Human beings have 23 different chromosomes, so the number of possible combinations iswhich is over 8 million.
Anaphase I The homologous chromosomes in each bivalent are separated and move to the opposite poles of the cell Telophase I The chromosomes become diffuse and the nuclear membrane reforms.
Cytokinesis The final cellular division to form two new cells, followed by Meiosis II. Meiosis I is a reduction division: The events of Meiosis II are analogous to those of a mitotic division, although the number of chromosomes involved has been halved. Meiosis generates genetic diversity through: