macronucleus

mac·ro·nu·cle·us

M0015800 (măk′rō-no͞o′klē-əs, -nyo͞o′-)n. pl. mac·ro·nu·cle·i (-klē-ī′) The larger of two nuclei present in ciliate protozoans, which controls nonreproductive functions of the cell, such as metabolism.

mac′ro·nu′cle·ar adj.

macronucleus

(ˌmækrəʊˈnjuːklɪəs) n, pl -clei (-klɪˌaɪ) (Microbiology) the larger of the two nuclei in ciliated protozoans. Compare micronucleus

mac•ro•nu•cle•us

(ˌmæk roʊˈnu kli əs, -ˈnyu-)

n. the larger of the two types of nuclei in ciliate protozoans, functioning in cell metabolism. Compare micronucleus. [1890–95] mac`ro•nu′cle•ar, adj.

Macronucleus

enUK

macronucleus

[¦mak·rō′nü·klē·əs] (invertebrate zoology) A large, densely staining nucleus of most ciliated protozoans, believed to influence nutritional activities of the cell.

Macronucleus

the larger (somatic) nucleus in infusorians (ciliate protozoan).

In most ciliate protozoans, the macronucleus is highly polyploid—that is, it contains several dozen to several thousand sets of chromosomes. It divides by fission and, less often, by budding, in which case full chromosome sets are distributed between the daughter nuclei. During sexual reproduction (conjugation), the macronucleus disintegrates and is replaced by a new macronucleus, which develops from the generative nucleus, or micronucleus. When this happens (and also at every division), the chromosome sets of the macronucleus multiply by endomitosis, the autonomous doubling of the number of chromosomes. The genetic apparatus of the macronucleus is active, synthesizing all types of ribonucleic acid and directing all biosynthetic processes in the cell. In the lower multinucleate infusorians, the macronuclei remain diploid and are incapable of dividing. With each division of the organism, the macronuclei are distributed between the daughter cells, resulting in a decrease in their number, and the missing macronuclei are regenerated by the micronuclei.

I. B. RAIKOV

See Macronucleus

macronucleus

mac·ro·nu·cle·us

(mak'rō-nū'klē-ŭs), 1. A nucleus that occupies a relatively large portion of the cell, or the larger nucleus where two or more are present in a cell.
See also: micronucleus (2). Synonym(s): meganucleus2. The larger of the two nuclei in ciliates, which governs vegetative metabolic functions and not reproduction.
See also: micronucleus (2). Synonym(s): somatic nucleus, trophic nucleus, trophonucleus

macronucleus

(măk′rō-no͞o′klē-əs, -nyo͞o′-)n. pl. macronu·clei (-klē-ī′) The larger of two nuclei present in ciliate protozoans, which controls nonreproductive functions of the cell, such as metabolism.

mac′ro·nu′cle·ar adj.

mac·ro·nu·cle·us

(mak'rō-nū'klē-ŭs) 1. A nucleus that occupies a relatively large portion of the cell, or the larger nucleus where two or more are present in a cell. 2. The larger of the two nuclei in ciliates, which governs vegetative metabolic functions and not reproduction.
See also: micronucleus (2)

macronucleus

meganucleus

the larger of two nuclei found in some PROTOZOANS, that is concerned with cell division (see MICRONUCLEUS). It disappears during CONJUGATION and is afterwards reformed from material of micronuclear origin (from the zygote nucleus). It appears to have mainly vegetative functions.

单词	macronucleus
释义	macronucleus enUK mac·ro·nu·cle·us M0015800 (măk′rō-no͞o′klē-əs, -nyo͞o′-)n. pl. mac·ro·nu·cle·i (-klē-ī′) The larger of two nuclei present in ciliate protozoans, which controls nonreproductive functions of the cell, such as metabolism. mac′ro·nu′cle·ar adj. macronucleus (ˌmækrəʊˈnjuːklɪəs) n, pl -clei (-klɪˌaɪ) (Microbiology) the larger of the two nuclei in ciliated protozoans. Compare micronucleus mac•ro•nu•cle•us (ˌmæk roʊˈnu kli əs, -ˈnyu-) n. the larger of the two types of nuclei in ciliate protozoans, functioning in cell metabolism. Compare micronucleus. [1890–95] mac`ro•nu′cle•ar, adj. Macronucleus enUK macronucleus [¦mak·rō′nü·klē·əs] (invertebrate zoology) A large, densely staining nucleus of most ciliated protozoans, believed to influence nutritional activities of the cell. Macronucleus the larger (somatic) nucleus in infusorians (ciliate protozoan). In most ciliate protozoans, the macronucleus is highly polyploid—that is, it contains several dozen to several thousand sets of chromosomes. It divides by fission and, less often, by budding, in which case full chromosome sets are distributed between the daughter nuclei. During sexual reproduction (conjugation), the macronucleus disintegrates and is replaced by a new macronucleus, which develops from the generative nucleus, or micronucleus. When this happens (and also at every division), the chromosome sets of the macronucleus multiply by endomitosis, the autonomous doubling of the number of chromosomes. The genetic apparatus of the macronucleus is active, synthesizing all types of ribonucleic acid and directing all biosynthetic processes in the cell. In the lower multinucleate infusorians, the macronuclei remain diploid and are incapable of dividing. With each division of the organism, the macronuclei are distributed between the daughter cells, resulting in a decrease in their number, and the missing macronuclei are regenerated by the micronuclei. I. B. RAIKOV See Macronucleus macronucleus enUK mac·ro·nu·cle·us (mak'rō-nū'klē-ŭs), 1. A nucleus that occupies a relatively large portion of the cell, or the larger nucleus where two or more are present in a cell. See also: micronucleus (2). Synonym(s): meganucleus2. The larger of the two nuclei in ciliates, which governs vegetative metabolic functions and not reproduction. See also: micronucleus (2). Synonym(s): somatic nucleus, trophic nucleus, trophonucleus macronucleus (măk′rō-no͞o′klē-əs, -nyo͞o′-)n. pl. macronu·clei (-klē-ī′) The larger of two nuclei present in ciliate protozoans, which controls nonreproductive functions of the cell, such as metabolism. mac′ro·nu′cle·ar adj. mac·ro·nu·cle·us (mak'rō-nū'klē-ŭs) 1. A nucleus that occupies a relatively large portion of the cell, or the larger nucleus where two or more are present in a cell. 2. The larger of the two nuclei in ciliates, which governs vegetative metabolic functions and not reproduction. See also: micronucleus (2) macronucleus or meganucleus the larger of two nuclei found in some PROTOZOANS, that is concerned with cell division (see MICRONUCLEUS). It disappears during CONJUGATION and is afterwards reformed from material of micronuclear origin (from the zygote nucleus). It appears to have mainly vegetative functions.
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