The discovery of anaphase

DEFINITION

Anaphase is the stage of mitosis or meiosis in which the chromosomes move from the equatorial plate toward the poles of the cell. In mitosis a full set of daughter chromosomes (46 in humans) moves toward each pole. In the first division of meiosis one memeber of each homologous pair (23 in humans), consisting of two chromatids united at the centromere, moves toward each pole. In the second division of meiosis the centromere divides and the two chromatids separate with one moving to each pole[1].

DISCOVERY

The Russian embryologist Alexander Onufrievich Kovalevsky discovered[2] anaphase in 1871 while studying embryos of the Rhynchelmis genus of worms. He used chromic acid to harden the embryos in order to observe them more clearly. In his 1871 publication, he records the development of the embryos in question and observed the instance before the first cell division took place. He notes that the “two granular clusters” (which were indeed chromosomes) were connected to each other by “protoplasmic strands” (which were indeed microtubules). Here is his original illustration of his observation:

DISCOVERER

Here is a portrait[3] of Alexander Onufrievich Kovalevsky:

1840-1901

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