chiasma

genetics

Also known as: chiasmata

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June 24, 2026

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In genetics, a chiasma (plural: chiasmata) is a cross-shaped configuration of paired chromatids that is visible during a specific stage of meiosis. This structure is considered the cytological evidence of genetic crossing-over.1

Meiosis is a specialized type of cell division that produces genetically distinct haploid cells, such as gametes. During prophase I of meiosis, homologous chromosomes pair up. It is at this stage that crossing-over occurs, where segments of genetic material are exchanged between these paired chromosomes. This exchange of genetic material is a primary mechanism for introducing variation into populations. The chiasma is the physical manifestation of this genetic recombination.23415

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heredity
Simple linkage
Furthermore, Morgan perceived that the chiasmata (crosses that occur in meiotic chromosomes) indicate the mechanism underlying the phenomena of linkage and crossing over. As shown schematically in the diagram of chromosomes at meiosis, the maternal and paternal chromosomes (represented in blue and red) cross over and exchange segments, so a…
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Furthermore, Morgan perceived that the chiasmata (crosses that occur in meiotic chromosomes) indicate the mechanism underlying the phenomena of linkage and crossing over. As shown schematically in the diagram of chromosomes at meiosis, the maternal and paternal chromosomes (represented in blue and red) cross over and exchange segments, so a…
Read More