chromatid

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Related to Chromatids: Sister chromatids

chromatid

(krō`mətəd): see chromosomechromosome
, structural carrier of hereditary characteristics, found in the nucleus of every cell and so named for its readiness to absorb dyes. The term chromosome
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; crossing overcrossing over,
process in genetics by which the two chromosomes of a homologous pair exchange equal segments with each other. Crossing over occurs in the first division of meiosis. At that stage each chromosome has replicated into two strands called sister chromatids.
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.

Chromatid

 

one of the components of a chromosome, formed in the nucleus during the interphase of the cell nucleus as a result of the chromosome’s duplication. In mitosis, each chromosome consists of two chromatids; after separating into the daughter nuclei, each chromatid becomes an independent chromosome. In meiosis, homologous chromosomes come together in pairs to make up a four-chromatid structure, or tetrad.

According to the single-chain chromosome model, each chromatid contains in cross section a single tightly coiled and condensed double-strand molecule of deoxyribonucleic acid (DNA). In the multichain chromosome model, it is assumed that each chromatid contains in cross section several DNA molecules, in which case various types of chromatids are distinguished, such as semichromatids and quarter-chromatids. Most experiments have confirmed the single-chain model.

I. I. KIKNADZE

chromatid

[′krō·mə·təd]
(cell and molecular biology)
One of the pair of strands formed by longitudinal splitting of a chromosome which are joined by a single centromere in somatic cells during mitosis.
One of a tetrad of strands formed by longitudinal splitting of paired chromosomes during diplotene of meiosis.
References in periodicals archive ?
Cremediated recombination at the loxP sites between sister chromatids produced a dicentric and an acentric chromosome.
The SDR gametes contain sister chromatids from the centromere to the
There are several important mitosis restriction points, for example, formation of metaphase in equatorial plane or separation of sister chromatids during anaphase, in which Nek6 and Pttg1 genes play an important role.
It was possible to identify chromosomes with double B and/or G on the same chromatid, as also B and/or G in both sister chromatids.
When the mitotic cohesin protein RAD21 is expressed instead ofREC8 in yeast, sister chromatids undergo equational rather than reductional chromosomal segregation during meiosis I [55, 57].
This finding is in agreement with the conclusion that the counter-tension produced by the cleavage of the kleisin subunit of cohesin observed when all sister chromatids are in mitosis (Jones, 2010) or all bivalents are in meiosis (Dumont et al., 2010) follows the alignment of the chromosomes at the equator.
Melanomas that have gains and losses in chromosomal fragments have most likely reached a crisis stage, with binding of chromatids and uneven breakage during mitosis.
Meiosis in organisms with monocentric chromosomes is always pre-reductional, where the first division is reductional with segregation of the homologous chromosomes and the second division is equational with segregation of the sister chromatids. Halkka (1959) considered the post-reductional meiosis is the most primitive type of meiosis.
The peculiar characteristics of this meiotic system were efficiently used by Jones (1971) to analyze tritium-labelled meiotic chromosomes, and demonstrate convincingly that the origin of chiasmata was through breakage and rejoining of homologous nonsister chromatids, i.e., it is a validation of the chiasmatype theory (Janssens 1924).