Déconstruction

The genome is the whole of the genetic material of an individual or a Espèce. The Gène S constitute only part of the genome. This one consists of nucleic acid molecules of : DNA and ARN.

At the man, the nuclear genome is distributed on 46 Chromosome S, that is to say 22 pairs of Autosome S and two Gonosome S. One should not confuse the genome and the Caryotype, which characterizes the chromosomes.

  • At the Virus, the genome is contained either in a simple Molécule of DNA or double bit, or in a Molécule of ARN.

  • At the Procaryotic S (example: Bacterium S), one distinguishes the chromosomal genome, contents in a circular molecule of DNA, and the genome extrachromosomic, contained in Plasmide S and épisome S.
  • At the Eucaryote S, one distinguishes three types of genomes:
    • the nuclear genome (in the core);
    • the genome mitochondrial (in the Mitochondrion S), transmitted by the mother;
    • the genome chloroplastic (in the Chloroplast S), at the Plant S.

The science which studies the genome is the Génomique.

Cut genome

The size of the genome measures of number of Nucléotide S, or bases . Most of the time, one speaks about Pb (for even of bases , since the majority of the genomes consists of double bits of DNA or of ARN). One often employs the multiples kpb (for kilo-bases) or Mpb (méga-bases), which is worth 1  respectively; 000 and 1  000  000 bases. The size of the genome can be expressed in pg (pico-grams), which corresponds to the mass of DNA (haploid) per cell. 1 pg represents approximately 1  000 Mpb (978 Mpb precisely).

The size of the genome can vary few kilo-bases at the Virus to several hundreds of thousands of Mb at some Eucaryotes. The quantity of DNA, contrary to what was supposed a long time, is not proportional to the complexity of an organization; thus, the Ameba Ameba dubia , a unicellular organization, has a genome approximately 200 times larger than Homo sapiens . This report is frequently called Paradoxe of the value C.

The human genome was estimated at a little more 30  000 genes. This estimate was re-examined with the fall in 2004 and is now between 20  000 and 25  000 - a little less than Arabidopsis thaliana (27  000 genes).

The complete sequence of the last chromosome in the human genome (the chromosome 1, largest, container with him only 8% of this genome) was obtained in May 2006.

See also: Genetic human

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