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Schematic karyogram of the human chromosomes, showing their usual state in the G 0 and G 1 phase of the cell cycle. At top center it also shows the chromosome 3 pair in metaphase (annotated as "Meta."), which takes place after having undergone DNA synthesis which occurs in the S phase (annotated as S) of the cell cycle.
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.
Time-lapse video of mitosis in a Drosophila melanogaster embryo. The primary result of mitosis and cytokinesis is the transfer of a parent cell's genome into two daughter cells. The genome is composed of a number of chromosomes—complexes of tightly coiled DNA that contain genetic information vital for proper cell function. [32]
Prometaphase is the phase of mitosis following prophase and preceding metaphase in eukaryotic somatic cells.In prometaphase, the nuclear membrane breaks apart into numerous "membrane vesicles," and the chromosomes inside form protein structures called kinetochores. [1]
The presence of these core cell cycle factors can be explained through their role in neuronal migration, maturation, and synaptic plasticity (Christopher L. Frank1 and Li-Huei Tsai1, 2009). However, it is also possible that, under certain conditions, these factors can induce cell cycle re-entry.
[5] [6] After growth from the zygote to the adult, cell division by mitosis allows for continual construction and repair of the organism. [7] The human body experiences about 10 quadrillion cell divisions in a lifetime. [8] The primary concern of cell division is the maintenance of the original cell's genome.
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]
Lymphocytes can enter mitosis when they are activated by mitogens or antigens. B cells specifically can divide when they encounter an antigen matching their immunoglobulin . T cells undergo mitosis when stimulated by mitogens to produce small lymphocytes that are then responsible for the production of lymphokines , which are substances that ...