The present invention is directed generally to the use of stem-loop oligonucleotides comprising an inverted repeat, a loop, and at least one degradable site or site capable of becoming a degradable site in the preparation of DNA molecules, such as a library. In particular embodiments, the invention employs a single reaction mixture and conditions. In particular, at least part of the inverted palindrome is removed during the preparation of the molecules to facilitate amplification of the molecules. Thus, in specific embodiments, the DNA molecules are suitable for amplification and are not hindered by the presence of the palindrome.