Cell Life cycle

Diagram of the cell cycle: the Intef, orange, home to the G0 phase, S and G1, the M phase, however, only consists of mitosis and cytokinesis, if any.

The cell cycle is the orderly and repetitive in time by which a stem cell grows and divides into two daughter cells. The cells are not dividing are at a stage known as G0, parallel to the cycle. The cell cycle regulation is essential for the proper functioning of healthy cells, is clearly structured into fases
The state of not splitting or interface. The cell performs its specific functions and, if it is to move to cell division, begins by making the duplication of its DNA.
The state of division, called the M phase, a situation which includes mitosis and cytokinesis. Cytokinesis in some cells does not occur, resulting in cell division plurinucleada mass called a plasmodium.

Unlike what happens in mitosis, where the gene pool is maintained, there is a variant of cell division characteristic of the germ line cells, called meiosis. It reduces the diploid genetic background common to all somatic cells of the body, a haploid, that is, with one copy of the genome. Thus, fusion during fertilization, two haploid gametes from two different parent results in a zygote, a new individual, diploid equivalent in their genetic endowment padres.

G1 phase: the first phase of the cell cycle in which there is cell growth and protein synthesis of RNA. It is the period that elapses between the end of mitosis and initiating DNA synthesis. In it, the cell doubles in size and mass due to the continuous synthesis of all its components as a result of the expression of genes encoding proteins responsible for its particular phenotype.
Phase S: is the second phase of the cycle, which occurs in the replication or DNA synthesis. As a result, each chromosome is duplicated and is composed of two identical chromatids. With DNA replication, the nucleus contains twice as nuclear proteins and DNA in the beginning.

G2 phase: the second growth phase in the cell cycle that continues the synthesis of proteins and RNA. At the end of this period is observed under the microscope changes in cellular structure, which indicate the beginning of cell division. It ends when the chromosomes begin to condense at the beginning of mitosis.
The M phase is the phase of cell division in which a parent cell divides into two daughter cells identical to each other daughters and mother. This phase includes mitosis, in turn divided into: prophase, metaphase, anaphase, telophase and cytokinesis, which starts already in the mitotic telophase.

Improper regulation of cell cycle can lead to the development of precancerous cells that, if they are induced to commit suicide by apoptosis, can lead to cancer development. Failures leading to the deregulation are related to cellular genetics: what are the most common alterations in oncogenes, tumor suppressor genes and repair genes ADN.55

Source

The emergence of life, and therefore the cell, probably started by the transformation of inorganic into organic molecules under appropriate environmental conditions, leading to further interaction of these biomolecules generating entities of greater complexity. The Miller-Urey experiment, conducted in 1953 showed that a mixture of simple organic compounds can be transformed into some amino acids, carbohydrates and lipids (components of all living matter) under environmental conditions that simulate hypothetical present on early Earth (about Archean Eon)

It is postulated that the organic components were pooled to generate complex structures of Oparin's coacervates still acellular that once reached the ability to self-organize and perpetuate itself, gave rise to a primitive cell type, the progenote of Carl Woese, the predecessor of the types Once cellular diversified actuales.26 this cell group, giving rise to variants prokaryotes, archaea and bacteria, might appear new types of cells, more complex, endosymbiosis, that is, permanent collection of some other cell types without a loss aquéllos.57 total autonomy Thus, some authors describe a model in which the first eukaryotic cell arose by introduction of an arch inside a bacterium, resulting in this first of a primitive core celular.58 However, the inability of bacteria to carry out phagocytosis and therefore capture another type of cell, led to another hypothesis, which suggests a cell called a phagocyte cronocito which a bacterium and an archaeon, leading to the first eukaryotic organism. In this way, and by sequence analysis at the genomic level of eukaryotic model organisms, we have obtained original cronocito describe this as a body with cytoskeleton and plasma membrane, which bases its phagocytic capacity, and whose genetic material was RNA, This may explain, if the bows had phagocytized the DNA, the spatial separation between the existing eukaryotic transcription (nuclear) and translation (cytoplasmic) .

An additional difficulty is the fact that eukaryotes have been found originally as required amitocondriados endosymbiont hypothesis. In addition, the team of Maria Rivera, University of California, comparing whole genomes from all domains of life has found evidence that eukaryotes contain two different genomes, one more akin to bacteria and other archaea, pointing in the latter If similarities to methanogens, particularly in the case of histonas. This led Bill Martin and Miklós Müller to the hypothesis that eukaryotic cells arose by endosymbiosis not, but chimeric fusion and metabolic coupling of Methanogens and one α-proteobacteria symbionts through hydrogen (hydrogen hypothesis) This hypothesis today attracts very encotradas positions, with detractors as Christian de Duve.