Crossword clues for synapsis
Douglas Harper's Etymology Dictionary
plural synapses, 1895 in cellular biology, Modern Latin, from Greek synapsis "connection, junction" (see synapse).
Wiktionary
n. 1 The association of homologous maternal and paternal chromosomes during the initial part of meiosis. 2 (alternative form of synapse English)
WordNet
n. the side by side pairing of homologous maternal and paternal chromosomes at the start of meiosis
[also: synapses (pl)]
Wikipedia
Synapsis (also called syndesis) is the pairing of two homologous chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. Synapsis takes place during prophase I of meiosis. When homologous chromosomes synapse, their ends are first attached to the nuclear envelope. These end-membrane complexes then migrate, assisted by the extranuclear cytoskeleton, until matching ends have been paired. Then the intervening regions of the chromosome are brought together, and may be connected by a protein-RNA complex called the synaptonemal complex. While autosomes undergo synapsis during meiosis, sex chromosomes often remain unpaired.
This is not to be confused with mitosis. Mitosis also has prophase, but does not ordinarily do pairing of two homologous chromosomes.
When the non-sister chromatids intertwine, segments of chromatids with similar sequence may break apart and be exchanged in a process known as genetic recombination or "crossing-over". This exchange produces a chiasma, a region that is shaped like an X, where the two chromosomes are physically joined. At least one chiasma per chromosome often appears to be necessary to stabilise bivalents along the metaphase plate during separation. The crossover of genetic material also provides a possible defence against 'chromosome killer' mechanisms, by removing the distinction between 'self' and 'non-self' through which such a mechanism could operate. A further consequence of recombinant synapsis is to increase genetic variability within the offspring. Repeated recombination also has the general effect of allowing genes to move independently of each other through the generations, allowing for the independent concentration of beneficial genes and the purging of the detrimental.
Following synapsis, a type of recombination referred to as synthesis dependent strand annealing (SDSA) occurs frequently. SDSA recombination involves information exchange between paired non-sister homologous chromatids, but not physical exchange. SDSA recombination does not cause crossing-over. Both the non-crossover and crossover types of recombination function as processes for repairing DNA damage, particularly double-strand breaks (see Genetic recombination).
The central function of synapsis is therefore the identification of homologues by pairing, an essential step for a successful meiosis. The processes of DNA repair and chiasma formation that take place following synapsis have consequences at many levels, from cellular survival through to impacts upon evolution itself.
Usage examples of "synapsis".
Do any specific cells or synapses show changes which correspond to the behavioural adaptation?
The soreness lifted out of my muscles, and my cloudy, cloggy thought processes cleared as though someone had flushed my synapses with jalapeno.
Along the synapses of my brain, microscopic machines are implanting cultured oligodendrocytes, reversing the myelin-sheath breakdown along my neural pathways, disassembling the creaking old wetware threaded through my brain and CNS, grafting pluripotent stem cells into a collagen base to replace nerve tissue lost to injury and to scarring.
If skin presses skin with adequate firmness, the electrical synapses may be instantly established to transfer the orgasmic images.
I felt the insidious tilt at the corners of perception as the tetrameth went barrelling along my synapses, and when it was my turn to do Trepp I almost got lost in the geometries of her face.
This would mean that new learning corresponds to the generation of new synapses or the activation of moribund old ones, and some preliminary evidence consistent with this view has been obtained by the American neuroanatomist William Greenough of the University of Illinois and his coworkers.
For instance, the morphologists Mary Chen and Craig Bailey have spent several years studying and measuring the synapses of the Aplysia abdominal ganglion.
Then the filaments began to unwind from each other and porrect forward, their probing tips slowly winding their way round cells as they sought out synapses.
I had to go ahead without any significant foreplay, but I knew that he was wide awake, and I knew that he could tell himself, if it made it any easier for him, that it was only a delirious dream, only a hallucination, only some stray psychotropic protein making merry amid the synapses of his deluded brain.
As always, he pictured a lozenge of liver-like flesh nestled tumour-fashion at the heart of his brain, squirting out cold milky liquids into surrounding synapses.
Synapses could be strengthened like this by biochemically modifying their structure, or by changing their electrical properties, or by simple growth.
Ever since the first development of artificial synapses capable of linking up human nervous systems to silicon-based electronic systems, numerous schemes had been devised for hooking up the brain to computers or adding smart nanotech to its cytoarchitecture, but almost all the experiments had gone disastrously wrong.