tetrad

American  

[te-trad] / ˈtɛ træd /

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.

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tetrad British  

/ 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

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tetrad Scientific  

/ 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

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Etymology

Origin of tetrad

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

Example Sentences

We measured their dark tetrad traits using standard psychological tests.

From Salon

The Current Newspapers, the tetrad of hyperlocal printed newspapers in Northwest D.C., is in bankruptcy.

From Washington Post

It was the end of an eclipse series known as a lunar eclipse tetrad.

From Scientific American

Sunday will be the fourth appearance of a blood moon over the last two years, in what is known as a tetrad series.

From The Guardian

This weekend's blood moon will be the last in a series of four lunar eclipses, dubbed a tetrad, over the last two years.

From National Geographic