Polar increase and decrease - what does that mean (Jun/23/2010 )
I was reading this paper that mentions how a mutation caused a "polar decrease" in the transcription of a certain gene. I'd like to know what polar means in this context.
"Polar" in this context is refering to "upstream", "downstream", or "distal". So, for example, if you mutate a promoter that drives an operon, you'll have polar effects on all downstream genes, although those genes are wild-type (i.e. not mutant). The same type of distal effects can be seen if, for example, you mutate a repressor gene -- the genes which are effected by this protein will be de-repressed, although you've made no change (i.e. mutation) to them. Or, if you insetionally mutate a gene by inserting a transposon in it, and the transposon contains a transcriptional terminator, operonic genes downstream of the mutant one will be affected.
Thanks! That was very helpful.
So I presume the term is more often use in situations where a regulatory/promoter region blocks expression of multiple genes, because I thought if it involves only one gene, then one would not need to put the word "polar?" I understand the meaning I am just trying to specify if this term also applies to single gene expression changes.
If mutating a gene affects only that gene, then there are by definition no polar effects. If mutating the gene effects many scattered genes serving many different functions, a better term would be to say the mutation has "pleiotropic effects". "Polar effects" is used mostly to describe the effect a mutation has on nearby genes devoted to the same ultimate function, as in synthesis and assembly of a capsular polysaccharide, for example.