Loopable?

[a_modified_dog]

make use of setInterval -

TL = this; // reference to main timeline
arr = ["strandA","strandT","strandC","strandG"];

function bio(){
arr.sort(function(){return Math.floor(Math.random()*3)-1});
var clip = arr[0]; 
TL.attachMovie(clip,clip,1,init); 
};

bioInterval = setInterval(bio,3000);