In biology, phase variation is a method for dealing with rapidly varying environments without requiring random mutation. It involves the variation of protein expression, frequently in an on-off fashion, within different parts of a bacterial population. As such the phenotype can switch at frequencies that are much higher (sometimes >1%) than classical mutation rates. Phase variation contributes to virulence by generating heterogeneity. Although it has been most commonly studied in the context of immune evasion, it is observed in many other areas as well and is employed by various types of bacteria, including Salmonella species.
whoissaadis it the same thing as antigenic variation?+12
dorsomedial_nucleusNo, antigenic variation involves genomic rearrangement
Phase variation can be thought of as MORE or LESS of something. An on/off switch. No DNA is being rearranged, just under or overexpressed in response to the environment. +8
makinallkindzofgainzThis isn't in Zanki, Lightyear, or First Aid, and I don't remember ever learning about this in class. Thanks NBME! :D+21
jurrutiaYou wouldn't expect the difference in phenotype of a given organism in a given patient to change because of mutations. It has to be something other than mutation. Phase variation is the only option that sounded like non-mutation. +
l0ud_minorityOne of my lectures at my school covered this apparently. In one of their 150+ slide power point handouts small font on slide 65 bottom left hand corner.+1
ankigravityDon't know if it was in UWorld a year ago, but there is a UWorld question about phase variation. I made card from it stating, "{{c1::Phase}} variation refers to a reversible switch between an “all-or-none” (on/off) expressing phase, resulting in variation in the level of expression of one or more proteins between individual cells of a clonal population."+1
submitted by ∗yotsubato(1208)
In biology, phase variation is a method for dealing with rapidly varying environments without requiring random mutation. It involves the variation of protein expression, frequently in an on-off fashion, within different parts of a bacterial population. As such the phenotype can switch at frequencies that are much higher (sometimes >1%) than classical mutation rates. Phase variation contributes to virulence by generating heterogeneity. Although it has been most commonly studied in the context of immune evasion, it is observed in many other areas as well and is employed by various types of bacteria, including Salmonella species.
https://www.wikiwand.com/en/Phase_variation