. Overlapping RNA fragments covering the entire genome of HIV-1 hxb2. PCR fragments of approximately 500 bp, with overlaps of 250 bp, and covering the entire genome of HIV-1 hxb2 were in vitro transcribed with T7 RNA polymerase into a set of uncapped and unpolyadenylated RNA fragments. After purification RNA fragments were migrated on Agilent-2100 Small RNA chips. A ladder on the left indicates the size in nucleotides.