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In this diagram of a duplicated chromosome, (2) identifies the centromere—the region that joins the two sister chromatids, or each half of the chromosome. In prophase of mitosis, specialized regions on centromeres called kinetochores attach chromosomes to spindle fibers. The centromere links a pair of sister chromatids together during cell ...
Human centromeres usually consist of 2000–4000 kilobases of a 171 base pair repeat unit. This alpha satellite is not present at all in human neocentromeres. [10] By 2008, more than 90 reported cases of human neocentromeres were detected on marker chromosomes that experienced a loss of centromere, and a subsequent rearrangement. [10]
In the case of humans, the old centromere went defunct and a more recent form emerged near the modern position of human cen6 (size of 60 Mb). Such cases are known as Evolutionary New Centromeres (ENC). This assembly phenomenon of the human chromosome 6 gives researchers an opportunity to investigate the origin of the ENC on chromosome 6. [4]
Nevertheless, it is clear that the presence of an excess of centrosomes is a common event in human tumors. It has been observed that loss of the tumor-suppressor p53 produces superfluous centrosomes, [25] as well as deregulating other proteins implicated in cancer formation in humans, such as BRCA1 and BRCA2. (For references, see [20].)
The largest regions on each chromosome are the short arm p and the long arm q, separated by a narrow region near the center called the centromere. [1] Other specific regions have also been defined, some of which are similarly found on every chromosome, while others are only present in certain chromosomes. Named regions include: Arms (p and q ...
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 ...
Compare sister chromatids to homologous chromosomes, which are the two different copies of a chromosome that diploid organisms (like humans) inherit, one from each parent. Sister chromatids are by and large identical (since they carry the same alleles, also called variants or versions, of genes) because they derive from one original chromosome.
The centromeres of the chromosomes convene themselves on the metaphase plate, an imaginary line that is equidistant from the two spindle poles. [3] This even alignment is due to the counterbalance of the pulling powers generated by the opposing kinetochore microtubules, [ 4 ] analogous to a tug-of-war between two people of equal strength ...