Methods and compositions are provided for amplifying a pool of oligonucleotides, such as dual guide oligonucleotide constructs comprising sequences encoding a first guide RNA segment and a sequence encoding a second guide RNA segment. An amplification mixture is formed comprising the pool of oligonucleotides, an amplification enzyme, deoxyribonucleotide triphosphates, and primers. The amplification mixture is thermocycled a sufficient number of times and under conditions to produce a library of oligonucleotide constructs. The present methods and compositions provide dual guide libraries, including libraries that are essentially free of scrambled library members.