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Beneden, Edouard van

chromosomes cells sex cell

[ben eden] (1846–1910) Belgian embryologist and cytologist: discovered that the number of chromosomes per cell is constant for a particular species.

Van Beneden followed his father in taking charge of zoology teaching at Liège in 1870. His course of teaching was based largely on his own researches, which he did not publish, but one of his students published them after van Beneden’s death. He showed in the 1880s that the number of chromosomes is constant in the cells of an animal body (except the sex cells) and the number is characteristic of the species (eg 46 in each human cell). He worked particularly with the chromosomes in the cell nuclei of an intestinal worm from horses; these chromosomes are conveniently large and few (four in the body cells, two in the sex cells). He found that the chromosome number is not doubled in the formation of the sex cells (the ova and spermatozoa) so that these have only half the usual number (a process called meiosis). When they unite, the normal number is restored, with results in accord with work in genetics. In fact, van Beneden misinterpreted some of his observations, which were clarified by the work.

The 46 human chromosomes. The banding, characteristic of specific chromosomes, is developed by staining: magnified about 2500 times. The XY karyotype shows that this is a male.

Benedict, Ruth [next]

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