Chemosensation

Chemosensation is the process of detecting, processing, and responding to volatile and water-soluble stimuli in the environment. C. elegans has a sophisticated chemosensory system, with much of its nervous system devoted to this process. Detection of these stimuli can result in behavioral outputs such as avoidance of or attraction to the chemical. While physiological responses can include a switch in developmental programs to a dauer stage rather than continuing to reproductive maturity. The amphid (anterior) and phasmid (posterior) chemosensory organs mediate chemosensation. On a cellular level, detection and activation of the chemosensory systems occurs through G-protein coupled receptors (GPCRs), of which different combinations are expressed in each amphid sensory neuron. The combination of GPCRs direct the type of chemical sensed and the response of the animal to the stimulus.

Meiotic maturation

During female gamete production oocytes arrest during the diplotene stage of meiosis I before completing diakinesis and moving into meiosis II. In response to hormones, oocytes resume and complete meiosis to produce the final mature gametes. In C. elegans, meiotic maturation is triggered by major sperm protein through G-alpha-S-adenylate cyclase - protein kinase A (PKA) signaling and soma-to-germline communication.

Mitosis

Mitosis is part of the eukaryotic cell cycle and results in the production of two daughter cells each with a copy of the genome. The cell cycle itself is comprised of an interphase (made up of three stages G1, S, and G2) and the M (mitotic) phase. Cell growth, active transcription and translation, and DNA replication occur during interphase. During M phase duplicated DNA (chromatin) condense into sister chromatids (prophase); the nuclear envelop breaks down, kinetochore microtubles attach to the chromosomes and centrosomes are pushed to the poles of the growing spindle (prometaphase); the chromosomes are lined up on the metaphase plate (metaphase); sister chromatids are pulled to spindle poles at opposite ends of the cell (anaphase); the nuclear envelop is reformed and the chromatids decondense to chromatin (telophase); and the cell is cleaved into two by a contractile ring and the resolution of a cleavage furrow (cytokinesis). In some variant cell cycles nuclear division may not be followed by cell division, or G1 and G2 phases may be absent.