tetrad

[ te-trad ]

noun

1. a group of four.
2. the number four.
3. Cell Biology. a group of four chromatids formed by synapsis at the beginning of meiosis.
4. Chemistry. a tetravalent or quadrivalent element, atom, or group.

tetrad

/ ˈtɛtræd /

noun

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

/ tĕt′răd′ /

1. A four-part structure that forms during prophase I of meiosis and consists of two homologous chromosomes, each composed of two identical chromatids. During prophase I of meiosis, one chromosome exchanges corresponding segments of genetic material with the other chromosome in the tetrad in the process called crossing over.
2. See more at meiosis
3. A group of four cells, as of spores or pollen grains, formed from a parent cell by meiosis. As part of the process of spermatogenesis, a spermatocyte divides into a tetrad of four spermatids, cells which go on to develop into sperm.
4. See more at spermatogenesis

Word History and Origins

Origin of tetrad¹

1645–55; < Greek tetrad- (stem of tetrás ) group of four

Word History and Origins

Origin of tetrad¹

C17: from Greek tetras, from tettares four

Example Sentences

For instance, they referred to justice as the (Tetrad, or) group-of-four,12 and likewise for everything else.

From Project Gutenberg

During the tetrad division in the basidium nuclear reduction occurs.

From Project Gutenberg

The tetrad for the perfect figure—the cube, length, depth, and width.

From Project Gutenberg

Having sent for that Brhman, he learnt from him a tetrad of gths.

From Project Gutenberg

They are aborting members of the tetrad, and appear to have been used as food by the other spores.

From Project Gutenberg