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Prophase is the first stage of mitosis in animal cells, and the second stage of mitosis in plant cells. [10] At the start of prophase there are two identical copies of each chromosome in the cell due to replication in interphase. These copies are referred to as sister chromatids and are attached by DNA element called the centromere. [11]
Mitosis in an animal cell (phases ordered counter-clockwise), with G 1 labeled at left. The G 1 phase, gap 1 phase, or growth 1 phase, is the first of four phases of the cell cycle that takes place in eukaryotic cell division. In this part of interphase, the cell synthesizes mRNA and proteins in preparation for subsequent steps leading to mitosis.
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
Cell division by mitosis is an equational division which gives rise to genetically identical cells in which the total number of chromosomes is maintained. [1] Mitosis is preceded by the S phase of interphase (during which DNA replication occurs) and is followed by telophase and cytokinesis, which divide the cytoplasm, organelles, and cell ...
The leptotene stage, also known as leptonema, is the first of five substages of prophase I during meiosis, the specialized cell division that reduces the chromosome number by half to produce haploid gametes in sexually reproducing organisms.
At the end of G2, the cell transitions into mitosis, where the nucleus divides. The G2 to M transition is dramatic; there is an all-or-nothing effect, and the transition is irreversible. This is advantageous to the cell because entering mitosis is a critical step in the life cycle of a cell.
The cell cycle is a series of complex, ordered, sequential events that control how a single cell divides into two cells, and involves several different phases. The phases include the G1 and G2 phases, DNA replication or S phase, and the actual process of cell division, mitosis or M phase. [1]
An aster is a cellular structure shaped like a star, consisting of a centrosome and its associated microtubules during the early stages of mitosis in an animal cell. [1]: 221 Asters do not form during mitosis in plants. Astral rays, composed of microtubules, radiate from the centrosphere and look like a cloud. Astral rays are one variant of ...