ActionScript 3 :: Instantiate New Object From Class Instance?

How can I instantiate another class object from a class instance? In the code below (which doesn't work) I'd like the function to return a new class instance based the passed argument's class. In other words, I want the function to return a new instance of MySprite without having to call new MySprite();.

var mySprite:Sprite = new MySprite();
var anotherSprite:Sprite = makeAnotherSprite(mySprite);
function makeAnotherSprite(instance:Sprite):Sprite {
return new getDefinitionByName(getQualifiedClassName(instance));
}