chiasma
/kʌɪˈazmə
/ /kɪˈazmə/noun (plural chiasmata /kʌɪˈazmətə/ /kɪˈazmətə/)
1 (also optic chiasma) Anatomy The X-shaped structure formed at the point below the brain where the two optic nerves cross over each other.The dura that invests the optic chiasma can be traced from the chiasma along the optic nerve.
2 Biology A point at which paired chromosomes remain in contact during the first metaphase of meiosis, and at which crossing over and exchange of genetic material occur between the strands.A given factor s can affect the recombination rate r through a change in the number of chiasmata occurring during meiosis....
- However, the observed differences may be conditional on the chromosomal location of the chiasmata.
- First, it generates crossovers between homologous chromosomes that mature into visible chiasmata.
Origin
Mid 19th century: modern Latin, from Greek chiasma 'crosspiece, cross-shaped mark', from khiazein 'mark with the letter chi'.
- have a tin ear
- have a way with
- have a way with one
- have a whale of a time
- have a will of one's own
- have a word
- have a word in someone's ear
- have bats in the (or one's) belfry
- have-been
- have been around
- have been around the block (a few times)
- have been known to do something
- have been there before
- have blood on one's hands
- have clean hands
- have designs on
- have every confidence in
- have everything
- have eyes bigger than one's stomach (or belly)
- have eyes in the back of one's head
- have eyes like a hawk
- have eyes like saucers
- have got
- have-got
- have (got) a good head on one's shoulders