micronucleusn.
/ˌmʌɪkrə(ʊ)ˈnjuːklɪəs/, U.S. /ˌmaɪkroʊˈn(j)ukliəs/ Zoology and Biology.
Originally: the smaller of the two types of nucleus of ciliate protozoans, which is involved in sexual reproduction. Later also: any relatively or abnormally small nucleus.
ΚΠ
1887 Jrnl. Royal Microsc. Soc. 7 973 According to Maupas the micronucleus is a hermaphrodite sexual element, of sole importance in conjugation.
1892 J. A. Thomson Outl. Zool. 101 In the ciliated Infusorians there are two nuclear bodies... The smaller or micro-nucleus lies by the side of the larger or macro-nucleus.
1901 G. N. Calkins Protozoa 194 The micronuclei play the most important part in conjugation.
1946 Nature 23 Nov. 750/1 The micronucleus is a small spherical structure situated in the neighbourhood of the macronucleus.
1964 M. Hynes Med. Bacteriol. (ed. 8) xxviii. 436 Stained preparations [of Trypanosoma gambiense] show two nuclear structures; the one, larger and centrally placed, is known as the macronucleus or trophonucleus and the other, smaller, placed at the posterior end, is known as the micronucleus or kinetoplast.
1984 J. W. Deacon Introd. Mod. Mycol. (ed. 2) viii. 128 (caption) Chromosomes lost from the aneuploid nuclei during successive mitotic divisions may ultimately reside in micronuclei.
1994 Life Extension Rep. May 37/3 Perhaps the most significant biomarker of developing lung cancer are bronchial micronuclei—the byproducts of mutational events in DNA that are a dynamic reflection of the malignancy process in the lung.
This entry has been updated (OED Third Edition, December 2001; most recently modified version published online March 2022).
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