Chromosome

:For information about chromosomes in genetic algorithms, see Chromosome (genetic algorithm).

Related Topics:
Genetic algorithm - Chromosome (genetic algorithm)

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The DNA which carries genetic information in biological cells is normally packaged in the form of one or more large macromolecules called chromosomes.

Related Topics:
DNA - Genetic information - Biological cell - Macromolecule

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A chromosome (in Greek chroma = color and soma = body) is, minimally, a very long, continuous piece of DNA, which contains many genes, regulatory elements and other intervening nucleotide sequences. In the chromosomes of eukaryotes, the uncondensed DNA exists in a quasi-ordered structure inside the nucleus, where it wraps around histones (structural proteins, Fig. 1), and where this composite material is called chromatin. During mitosis (cell division), the chromosomes are condensed and a spindle composed of microtubules is formed. Microtubules are self- assembled from dimers of alpha and beta tubulin. Microtubules attach to chromosomes at specialized structures, the kinetochores, one of which is present on each sister chromatid. The unfortunate term, "centromere" is sometimes used. There is no such structure. It is true that sister chromatids are attached to each other all along their lengths by proteins called cohesins. A special DNA base sequence in the region of the kinetochores provides, along with special proteins, longer- lasting attachment in this region. This is the only natural context in which individual chromosomes are visible with an optical microscope. Each chromosome has two arms, the shorter one called p arm (from the French petit, small) and the longer one q arm (q following p in the alphabet). Prokaryotes do not possess histones or nuclei. In its relaxed state, the DNA can be accessed for transcription, regulation, and replication.

Related Topics:
Greek - Gene - Regulatory element - Nucleotide sequences - Eukaryote - Nucleus - Histone - Protein - Chromatin - Mitosis - Microscope - French - Prokaryote - Transcription - Replication

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Chromosomes were first observed by Karl Wilhelm von Nägeli in 1842 and their behavior later described in detail by Walther Flemming in 1882. In 1910, Thomas Hunt Morgan proved that chromosomes are the carriers of genes.

Related Topics:
Karl Wilhelm von Nägeli - 1842 - Walther Flemming - 1882 - 1910 - Thomas Hunt Morgan

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