tetrad

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Related to Tetrads: meiosis

tetrad

1. a group or series of four
2. the number four
3. Botany a group of four cells formed by meiosis from one diploid cell
4. Genetics a four-stranded structure, formed during the pachytene stage of meiosis, consisting of paired homologous chromosomes that have each divided into two chromatids
5. Chem an element, atom, group, or ion with a valency of four
6. Ecology a square of 2 × 2 km used in distribution mapping

Tetrad

 

(1) A group of four haploid cells formed by meiosis from a single diploid cell. Tetrads are typical of plants. In mosses, fungi, and algae, such four-celled groups may remain for a long time within the membrane of the parent cell. By isolating the cells of the tetrad in these organisms, vegetative offspring may be obtained and the genetic division in each meiosis may be studied by means of tetrad analysis. Ordered arrangements of cells may occur in tetrads; the chromosome groups in the cells of such tetrads reflect the order in which the chromosomes of two successive meioses separate. These cells, called linear asci, are typical of some ascomycete fungi.

(2) In tetrad analysis, the four cultures obtained by the vegetative propagation of spores formed after the meiosis of a single diploid cell.

(3) A structure composed of four connected chromatids. It is observed in animal cells during the prophase of the first, or reductive, division of meiosis. Such tetrads are also called bivalents.

I. I. TOLSTORUKOV

tetrad

[′te‚trad]
(cell and molecular biology)
A group of four chromatids lying parallel to each other as a result of the longitudinal division of each of a pair of homologous chromosomes during the pachytene and later stages of the prophase of meiosis.
References in periodicals archive ?
Pro-orbicules, after exocytosis and generally during tetrad stage, nest on the tapetal plasmalemma, and it is on this lipidic surface that they receive their sporopollenin coat.
Carrion crow was the most widespread species, occurring in 93% of tetrads.
In this study, spore tetrads were found up to 10 m from a source plant, with most tetrads lodged within 30-100 cm.
Number of isolated total lunar eclipses and tetrads per century Years ITLEs Tetrads 0 to 99 0 0 100 to 199 2 3 200 to 299 2 6 300 to 399 5 4 400 to 499 2 3 500 to 599 0 0 600 to 699 0 0 700 to 799 2 3 800 to 899 3 7 900 to 999 3 7 1000 to 1099 2 0 1100 to 1199 0 0 1200 to 1299 1 0 1300 to 1399 3 6 1400 to 1499 5 4 1500 to 1599 3 6 1600 to 1699 0 0 1700 to 1799 0 0 1800 to 1899 2 0 1900 to 1999 2 5 2000 to 2099 1 8 2100 to 2199 3 4 2200 to 2299 0 0 2300 to 2399 0 0 2400 to 2499 1 4 2500 to 2599 3 7 2600 to 2699 2 8 2700 to 2799 1 0 2800 to 2899 0 0 2900 to 2999 1 1 3000 to 3099 2 5 3100 to 3199 2 8 3200 to 3299 3 3 3300 to 3399 0 0 3400 to 3499 0 0 3500 to 3599 1 2 3600 to 3699 3 6 3700 to 3799 2 6 3800 to 3899 1 1 3900 to 3999 0 0
From the metricity condition of the tetrad (with respect to the basis of [E.
Initial testing for thrombocytopenia included a peripheral blood smear, which showed intraerythrocytic ring forms and tetrads and a parasitemia level of 0.
The precocious initiation of cytokinesis, if occurring in algal-plant transitional forms, could in itself account for cryptospores, the oldest fossil spores, which seem to be imperfectly divided tetrads enclosed by a synoecosporal wall.
PZ: So you are suggesting thinking in tetrads enables pattern recognition, and resembles mythic thinking.
There are two ways to take part in Atlas fieldwork: choose one or more tetrads (a 2x2km square used by biologists for reporting distribution of species) to do four timed visits a season; or collate lists, anytime, anywhere to submit as roving records.
The atlas divides Britain and Ireland into 10km squares, with volunteers visiting tetrads of two by two kilometres in the squares.
Consideration of tetrads is important because it allows us to theorize the dynamics involved in the interaction of multiple-firms with multiple-firms (e.
AR177 is a novel oligonucleotide which is capable of folding upon itself to form an octet structure stabilized by the formation of two stacked guanosine tetrads.