Methods for producing a linear deoxyribonucleic acid (DNA) product with enhanced resistance to nuclease digestion are provided. The methods comprise, (a) digesting a double-stranded DNA molecule with an endonuclease that cleaves an endonuclease target sequence to generate a digested double-stranded DNA molecule, wherein the digested double-stranded DNA molecule comprises a linear double-stranded region, and a truncated protelomerase sequence at a first end, wherein the truncated protelomerase target sequence is non-functional; (b) appending a first adaptor molecule to the first end of the digested double-stranded DNA molecule and appending a second adaptor molecule to the second end of the digested double-stranded DNA molecule to generate a precursor double-stranded DNA molecule, wherein the first adaptor molecule comprises a truncated protelomerase target sequence that forms a first functional protelomerase target sequence with the truncated protelomerase sequence at the first end of the digested double-stranded DNA molecule; and (c) incubating the precursor double-stranded DNA molecule with a protelomerase to generate the linear DNA product, wherein the protelomerase closes the first end of the precursor double-stranded DNA molecule at the first functional protelomerase target sequence.