, ▁the ▁possibility ▁exists ▁that ▁this ▁mut ation ▁will ▁persist ▁within ▁the ▁population . ▁The ▁possibility ▁also ▁exists ▁that ▁the ▁change ▁in ▁function ▁becomes ▁advantage ous . ▁In ▁either ▁case , ▁while ▁being ▁subject ed ▁to ▁the ▁processes ▁of ▁natural ▁selection , ▁the ▁point ▁mut ation ▁has ▁been ▁accepted ▁into ▁the ▁gen etic ▁pool . ▁ ▁The ▁ 2 0 ▁am ino ▁ac ids ▁translated ▁by ▁the ▁gen etic ▁code ▁vary ▁greatly ▁by ▁the ▁physical ▁and ▁chemical ▁properties ▁of ▁their ▁side ▁ch ains . ▁However , ▁these ▁am ino ▁ac ids ▁can ▁be ▁categor ised ▁into ▁groups ▁with ▁similar ▁phys ico chem ical ▁properties . ▁Sub st itut ing ▁an ▁am ino ▁acid ▁with ▁another ▁from ▁the ▁same ▁category ▁is ▁more ▁likely ▁to ▁have ▁a ▁smaller ▁impact ▁on ▁the ▁structure ▁and ▁function ▁of ▁a ▁protein ▁than ▁replacement ▁with ▁an ▁am ino ▁acid ▁from ▁a ▁different ▁category . ▁Con sequently , ▁accept ance ▁of ▁point ▁mut ations ▁depends ▁heavily ▁on ▁the ▁am ino ▁acid ▁being ▁replaced ▁in ▁the ▁mut ation , ▁and ▁the ▁replacement ▁am ino ▁acid . ▁The ▁P AM ▁matrices ▁are ▁a ▁mathematical ▁tool ▁that ▁account ▁for ▁these ▁varying ▁rates ▁of ▁accept ance ▁when ▁evalu ating ▁the ▁similarity ▁of ▁prote ins ▁during ▁alignment . ▁ ▁Term in ology ▁The ▁term ▁accepted ▁point ▁mut ation ▁was ▁initially ▁used ▁to ▁describe ▁the ▁mut ation ▁phenomen on . ▁However , ▁the ▁ac ron ym ▁P AM ▁was ▁preferred ▁over ▁AP M ▁due ▁to ▁read ability , ▁and ▁so ▁the ▁term ▁point ▁accepted ▁mut ation ▁is