tetrad

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tetrad

 [tet´rad]
a group of four similar or related entities, as (1) any element or radical having a valence, or combining power, of four; (2) a group of four chromosomal elements formed in the pachytene stage of the first meiotic prophase; (3) a square of cells produced by division into two planes of certain cocci (Sarcina).
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

tet·rad

(tet'rad),
1. A collection of four things having something in common, such as a deformity with four features, for example, Fallot tetralogy. Synonym(s): tetralogy
2. In chemistry, a quadrivalent element.
3. In heredity, a bivalent chromosome that divides into four chromatids during meiosis.
[G. tetras (tetrad-), the number four]
Farlex Partner Medical Dictionary © Farlex 2012

tetrad

(tĕt′răd′)
n.
1. A group or set of four.
2. A tetravalent atom, radical, or element.
3. Biology
a. A four-part structure that forms during the prophase of meiosis and consists of two homologous chromosomes, each composed of two sister chromatids.
b. A group of four haploid cells, such as spores, formed by meiotic division of one mother cell.

te·trad′ic adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

tet·rad

(tet'rad)
1. A group of four things having something in common, such as a deformity with four features, e.g., Fallot tetralogy.
Synonym(s): tetralogy.
2. chemistry A quadrivalent element.
3. genetics A bivalent chromosome that divides into four during meiosis.
[G. tetras (tetrad-), the number four]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

tetrad

  1. the four homologous CHROMATIDS which associate during prophase (the PACHYTEN stage) and metaphase of MEIOSIS and are involved in CROSSING OVER.
  2. the four haploid cells produced by one complete meiotic division.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

tet·rad

(tet'rad)
Collection of four things having something in common, such as a deformity with four features, e.g., tetralogy of Fallot.
[G. tetras (tetrad-), the number four]
Medical Dictionary for the Dental Professions © Farlex 2012
References in periodicals archive ?
The size of [T.sub.4] tetrad effect values in all of the bauxite samples from different parts of the horizon with the computed values of AWI% for the first, second, third, and fourth tetrads are illustrated in Figure 11, Figure 12, Figure 13, and Figure 14, respectively.
For example, the syn dG16 in the middle tetrad of the TA(htel-21) and the syn dG15 in one of the terminal tetrads of the TA(htel-21)TT GQs greatly stabilized their respective major topologies, according to Phan et al.
Cytokinesis in microsporocyte meiosis is of the simultaneous type, and the micropore tetrads are tetrahedral.
The tetrad is an analytical model created by McLuhan to facilitate the translation of user experiences of media.
In 1493, a tetrad saw the expulsion of Jews by the Catholic Spanish Inquisition.
Making the latest tetrad more significant for some is the fact that it takes place at the end of a Shemitah cycle -- the seven-year period leading to God's commandment for resting the land and release of debts in Israel.
Some religions believe that a blood moon tetrad marks the beginning of terrible events.
Hagee wrote that every time a "tetrad" occurs during Jewish holy days, something "world-changing" and tragic happens to Israel.
Carrion crow was the most widespread species, occurring in 93% of tetrads. Wren and Chaffinch were second and third.
Initial testing for thrombocytopenia included a peripheral blood smear, which showed intraerythrocytic ring forms and tetrads and a parasitemia level of 0.4%.
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.