macronucleus

[mak-roh-noo-klee-uhs, -nyoo-]

noun

Biology.

1. the larger of the two types of nuclei nucleus occurring in ciliate protozoans, having a multiple set of chromosomes and functioning in cell metabolism and protein synthesis.

macronucleus

/ ˌmækrəʊˈnjuːklɪəs /

noun

1. the larger of the two nuclei in ciliated protozoans Compare micronucleus

Other Word Forms

• macronuclear adjective

Word History and Origins

Origin of macronucleus¹

From New Latin, dating back to 1890–95; macro-, nucleus

Example Sentences

There are three different sets of self-duplicating nuclei, with the DNA in each set serving different purposes: a large macronucleus, governing the events in regeneration after injury, a set of eight or more micronuclei containing the parts of the genome needed for reproduction, and great numbers of tiny nuclei from which the cilia arise.

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The clear spot to the right is the macronucleus, and the blobs are probably storage granules of some sort.

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In the centre lies a sizeable macronucleus, which stores the chromatin used for making the various genome products.

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The details of ciliate sex, and the behavior of the micronucleus and the macronucleus, differ slightly from one species to the next; my description is taken from the aforementioned Margulis and Schwartz, and also from Jönsson, F., Postberg, J. and Lipps, H. J. 2009.

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The macronucleus is made from the micronucleus, but it is not at all the same in content.

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