Cell communication (biology)
In cells, DNA is housed in the nucleus and it never leaves. The DNA within the nucleus is transcribed by tRNA, and the transcriptions of the DNA become RNA. The RNA (ribonucleic acid) leaves the nucleus to float freely around the cytoplasm, and it contains the instructions of the DNA that are vital to the coding, decoding, regulation and expression of genes. The ribosomes then take the RNA messages and turn them into proteins that build cells. When a virus enters a cell and inserts its DNA code into the nucleus, it gets transcribed and released into the cell for the ribosome to make it into a protein. This is how viral infections occur. The cell then explodes with the overproduction of the virus, releasing it into the body to infect any and all other cells it finds. It is theorized that through evolution, cells developed a defense system called RNAi (RNA interference) to stop the production of the proteins that have suspicious mirror image messages of the RNA. They don’t just destroy the suspicious messages, but the correct messages as well to stop all production of that message. This is a cell’s self-destruct mechanism and every cell, plant and animal, have RNAi: a way to turn off the production of a certain gene inside the protein.
Syllable
The "nucleus" is usually the vowel in the middle of a syllable. The "onset" is the sound or sounds occurring before the nucleus, and the "coda" (literally 'tail') is the sound or sounds that follow the nucleus. They are sometimes collectively known as the "shell". The term "rime" covers the nucleus plus coda. In the one-syllable English word "cat", the nucleus is "a" (the sound that can be shouted or sung on its own), the onset "c", the coda "t", and the rime "at". This syllable can be abstracted as a "consonant-vowel-consonant" syllable, abbreviated "CVC". Languages vary greatly in the restrictions on the sounds making up the onset, nucleus and coda of a syllable, according to what is termed a language's phonotactics.