Synapsis vs. Synapses

A while back, I ran into some confusion over synapsis and synapses in a paper I was editing. Below, I’ll untangle how these are used.

When talking about biology, synapsis refers to the exchange or crossover of chromosomes during meiosis.

In the context of neurology, a synapse refers to the connection point between two neurons. Less commonly, synapsis can also refer to a single synapse.

As a verb, synapse can be used for the forming of the connection between two neurons or for the process of chromosomes crossing over. And synapsed as an adjective refers to chromosomes that have gone through synapsis.

• “…chromosomes appear to condense normally … but fail to synapse and form chiasmata…”¹from Zetka, Monique C., Ichiro Kawasaki, Susan Strome, and Fritz Müller. “Synapsis and Chiasma Formation in Caenorhabditis Elegans Require HIM-3, a Meiotic Chromosome Core Component That Functions in Chromosome Segregation.” Genes & Development 13, no. 17 (September 1, 1999): 2258–70. http://genesdev.cshlp.org/content/13/17/2258.
• “Although PAIR2 signals were observed on both synapsed and unsynapsed chromosomes…”² from Nonomura, Ken-Ichi, Mutsuko Nakano, Mitsugu Eiguchi, Tadzunu Suzuki, and Nori Kurata. “PAIR2 Is Essential for Homologous Chromosome Synapsis in Rice Meiosis I.” Journal of Cell Science 119, no. 2 (January 15, 2006): 217–25. https://doi.org/10.1242/jcs.02736.

The point of confusion is that synapses is the plural of both synapsis and synapse. When talking about one pair of chromosomes interacting during meiosis, we want synapsis. With more than one pair, it’s synapses.

• “…anomalies in chromosomal synapses…”³from Ayarza, E., M. González, F. López, R. Fernández-Donoso, J. Page, and S. Berrios. “Alterations in Chromosomal Synapses and DNA Repair in Apoptotic Spermatocytes of Mus m. Domesticus.” European Journal of Histochemistry : EJH 60, no. 2 (June 14, 2016): 2677. https://doi.org/10.4081/ejh.2016.2677.

References

• Merriam-Webster Unabridged entries for synapse and synapsis
• Oxford English Dictionary entries for synapse and synapsis
• Webster’s New World/Stedman’s Concise Medical Dictionary (1987)
• Butterworths Medical Dictionary, 2nd Ed (1978)

• 1
  from Zetka, Monique C., Ichiro Kawasaki, Susan Strome, and Fritz Müller. “Synapsis and Chiasma Formation in Caenorhabditis Elegans Require HIM-3, a Meiotic Chromosome Core Component That Functions in Chromosome Segregation.” Genes & Development 13, no. 17 (September 1, 1999): 2258–70. http://genesdev.cshlp.org/content/13/17/2258.
• 2
  from Nonomura, Ken-Ichi, Mutsuko Nakano, Mitsugu Eiguchi, Tadzunu Suzuki, and Nori Kurata. “PAIR2 Is Essential for Homologous Chromosome Synapsis in Rice Meiosis I.” Journal of Cell Science 119, no. 2 (January 15, 2006): 217–25. https://doi.org/10.1242/jcs.02736.
• 3
  from Ayarza, E., M. González, F. López, R. Fernández-Donoso, J. Page, and S. Berrios. “Alterations in Chromosomal Synapses and DNA Repair in Apoptotic Spermatocytes of Mus m. Domesticus.” European Journal of Histochemistry : EJH 60, no. 2 (June 14, 2016): 2677. https://doi.org/10.4081/ejh.2016.2677.