First, Mike, welcome to the forums! I hope you enjoy the time you spend here. We're all a little nutty in our own way, but most of us are quite harmless. There's a lot of neat stuff to learn here, and a bunch of really knowledgeable and helpful folks to offer advice.
As to your question, this is from a discussion on your topic at subsim.com:
"The jumper wires that are such a distinctive part of most Second World War U-boats were in fact short-wave radio antennae (3-30MHz). Stretching both fore and aft of the conning tower, the forward portion was used to transmit while the stern twin wires were for reception. The antennae were connected to the radio within the U-boat by a thin insulated wire entering the conning tower facade. Coupled with their primary use was also the value of using the jumper wires as a means of attaching life lines for crew working on deck in bad weather."
Here's the link, if you want to follow it yourself:
http://www.subsim.com/radioroom/showthread.php?t=103494
As to how to replicate them, I've always found stretched sprue the easiest and most effective method. I pull it to a thickness that looks about right, then measure the lengths needed and attach them with regular white glue. I also use blobs of white glue (painted when dry) for the insulators. The glue is surprisingly strong unless your line takes a direct hit, and it's much easier to repair/redo (if necessary) than stuff like superglue.
I don't have any photos at the moment, but I'm working on Bronco's 1/350 Type IXc right now, and I'll be happy to post something once I'm done if it would help.
Good luck!