Can we apply for OD at JNTUK without original memos?

Yes, you can apply for OD at JNTUK without original memos. However, you will need the soft copies of your provisional certificate and original marks memo in a specific size. You will also need a scanned copy of your passport size photograph along with your scanned signature. 

There is another way to get your OD directly but it will cost you a little more than the online procedure. You can go to the university directly with the required documents and collect your OD.