Provided herein are methods and compositions for analyzing nucleic acids associated with single cells using nucleic acid barcodes. According to some embodiments, a method for producing one or more polynucleotides of interest comprises: obtaining a plurality of RNAs associated with one or more samples, wherein the samples are obtained from one or more subjects, each RNA is associated with a single sample, and the RNAs associated with each sample are present in a separate reaction volume; adding an adapter molecule to the RNAs associated with each sample, wherein the adapter molecule is generated using an enzymatic reaction and comprises a universal priming sequence, a barcode sequence, and a binding site; and incorporating the barcode sequence into one or more polynucleotides associated with each sample, thereby producing the one or more polynucleotides of interest.