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During the S-phase of each cell cycle (Figure 1), all of the DNA in a cell is duplicated in order to provide one copy to each of the daughter cells after the next cell division. The process of duplicating DNA is called DNA replication, and it takes place by first unwinding the duplex DNA molecule, starting at many locations called DNA ...
The second check point is in the G 2 phase, this checkpoint also checks for cell size but also the DNA replication. The last check point is located at the site of metaphase, where it checks that the chromosomes are correctly connected to the mitotic spindles. [ 17 ]
A pair of sister chromatids is called a dyad. A full set of sister chromatids is created during the synthesis phase of interphase, when all the chromosomes in a cell are replicated. The two sister chromatids are separated from each other into two different cells during mitosis or during the second division of meiosis.
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.
During cell division, the identical copies (called a "sister chromatid pair") are joined at the region called the centromere (2). Once the paired sister chromatids have separated from one another (in the anaphase of mitosis) each is known as a daughter chromosome. The short arm of the right chromatid (3), and the long arm of the right chromatid ...
In a diploid cell in G1 phase of the cell cycle, such a molecule is present in the form of the homologous chromosome. However, in the G2 phase of the cell cycle (following DNA replication), a second homologous DNA molecule is also present: the sister chromatid. Evidence indicates that, due to the special nearby relationship they share, sister ...
In a diploid cell there are two sets of homologous chromosomes of different parental origin (e.g. a paternal and a maternal set). During the phase of meiosis labeled “interphase s” in the meiosis diagram there is a round of DNA replication, so that each of the chromosomes initially present is now composed of two copies called chromatids ...
However, in order for the cell to function, proteins must be able to access the sequence information contained within the DNA, in spite of its tightly-packed nature. Hence, the cell has a number of mechanisms in place to control how DNA is organized. [4] Moreover, nuclear organization can play a role in establishing cell identity.