Diad

Diad is a term used in biology and genetics to refer to a pair of sister chromatids following chromosome duplication. This term is often used in the context of meiosis, a type of cell division that reduces the number of chromosomes in parent cells by half and produces four gamete cells.

Overview

During the process of meiosis, a diploid cell (one that contains two complete sets of chromosomes, one from each parent) undergoes two rounds of cell division to produce four haploid cells (cells with a single set of chromosomes). After the first round of DNA replication, each chromosome consists of two sister chromatids. These sister chromatids, or diads, are identical copies of one another and are held together at a region called the centromere.

Role in Meiosis

In the first division of meiosis, known as meiosis I, the diads line up along the metaphase plate during metaphase I. During anaphase I, the diads are pulled apart, with one chromatid going to each pole of the cell. This results in two daughter cells, each with a haploid set of chromosomes, but each chromosome still consists of two sister chromatids.

In the second division of meiosis, known as meiosis II, the sister chromatids within each chromosome are separated, resulting in four haploid cells, each with a single set of chromosomes.

See Also

• Tetrad (genetics)
• Chromosome
• Meiosis
• Centromere

References

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