jQuery: add dom element if it does not exist

Long question

Is it possible to add a DOM element only if it does not already exists?

Example

I have implemented the requirement like so:

var ins = $("a[@id='iframeUrl']");
ins.siblings('#myIframe:first').remove().end().parent().prepend('<iframe id="myIframe"  src="'+ins.attr("href")+'"></iframe>');

Is it possible to replace the second line with something more elegant? Like ins.siblings('#myIframe:first').is().not().parent().prepend ...

I could check ins.siblings('#myIframe:first').length and then add IFrame, but the curiosity took over and I'm trying to do that in the least amount of statements possible.