About 50% of patients with SARS-CoV-2 (causing COVID-19) experience some type of disorder associated with their sense of smell or taste, including ageusia and dysgeusia. SARS-CoV-1, MERS-CoV and even the flu (influenza virus) can also disrupt olfaction. History
Ayurveda, an ancient Indian healing science, has its own tradition of basic tastes, comprising sweet, salty, sour, pungent, bitter & astringent.In the West, Aristotle postulated in c. 350 BC that the two most basic tastes were sweet and bitter. He was one of the first identified persons to develop a list of basic tastes.The Ancient Chinese regarded spiciness as a basic taste. Research
The receptors for the basic tastes of bitter, sweet and savory have been identified. They are G protein-coupled receptors. The cells that detect sourness have been identified as a subpopulation that express the protein PKD2L1. The responses are mediated by an influx of protons into the cells but the receptor for sour is still unknown. The receptor for amiloride-sensitive attractive salty taste in mice has been shown to be a sodium channel. There is some evidence for a sixth taste that senses fatty substances.In 2010, researchers found bitter taste receptors in lung tissue, which cause airways to relax when a bitter substance is encountered. They believe this mechanism is evolutionarily adaptive because it helps clear lung infections, but could also be exploited to treat asthma and chronic obstructive pulmonary disease. == See also ==
A meiosis I error can result in isodisomic UPD if the gene loci in question crossed over, for example, a distal isodisomy would be due to duplicated gene loci from the maternal grandmother that crossed over and due to an error during meiosis I, ended up in the same gamete. A meiosis II error can result in heterodisomy UPD if the gene loci crossed over in a similar fashion. Phenotype
Most occurrences of UPD result in no phenotypical anomalies. However, if the UPD-causing event happened during meiosis II, the genotype may include identical copies of the uniparental chromosome (isodisomy), leading to the manifestation of rare recessive disorders. UPD should be suspected in an individual manifesting a recessive disorder where only one parent is a carrier. Uniparental inheritance of imprinted genes can also result in phenotypical anomalies. Although few imprinted genes have been identified, uniparental inheritance of an imprinted gene can result in the loss of gene function, which can lead to delayed development, intellectual disability, or other medical problems. The most well-known conditions include Prader–Willi syndrome and Angelman syndrome. Both of these disorders can be caused by UPD or other errors in imprinting involving genes on the long arm of chromosome 15. Other conditions, such as Beckwith–Wiedemann syndrome, are associated with abnormalities of imprinted genes on the short arm of chromosome 11.