chiasma

/kai'æzmə/

Thân thiện

The optic chiasma is visible in this anatomical diagram.

Definition

1. Noun:
   • An anatomical crossing point: A chiasma is a point where two structures, particularly nerve tracts or chromosomes, cross each other in an X-shaped formation.
   • A genetic crossover site: In genetics, a chiasma is the visible point of contact between paired homologous chromosomes during meiosis, where crossing over and exchange of genetic material occurs.

Usage and Examples

• Noun (Anatomical):
  • The optic chiasma is where the optic nerves from each eye partially cross.
  • A surgical procedure must carefully avoid damaging the chiasma of the nerve tracts.
• Noun (Genetic):
  • The formation of a chiasma is essential for genetic recombination.
  • Under the microscope, we could observe a chiasma between the paired chromosomes.

Advanced Usage

• "Chiasma formation": The process by which homologous chromosomes become linked at a crossover point during meiosis.
  • Chiasma formation is a prerequisite for proper chromosome segregation.
• "Chiasma frequency": The average number of chiasmata observed per cell during meiosis, often used as a measure of genetic recombination.
  • The chiasma frequency varies between different species and chromosomal regions.

Variants and Related Words

• Chiasm (n): An alternative, often synonymous, term for chiasma, especially in anatomical contexts.
  • The term 'optic chiasm' is more common than 'optic chiasma' in many textbooks.
• Chiasmal (adj): Pertaining to or of the nature of a chiasma.
  • The chiasmal region showed signs of inflammation.
• Chiasmatic (adj): Relating to a chiasma.
  • The chiasmatic cistern is a space in the brain near the optic chiasm.

Synonyms

• Crossing: A point where two things intersect (general term).
• Decussation: A technical term for an X-shaped crossing, especially of nerve fibers.
• Crossover: The point or process of exchange, particularly in genetics.

Related Terms and Concepts

• Synapsis: The pairing of homologous chromosomes, which precedes chiasma formation.
• Crossing over: The exchange of genetic material that occurs at a chiasma.
• Bivalent: The structure formed by a pair of homologous chromosomes held together by a chiasma.

Học thuật

Noun

1. an intersection or crossing of two tracts in the form of the letter X

Từ đồng nghĩa

• chiasm
• decussation