Compositions and methods for making guide nucleic acids

A method of preparing a library of nucleic acids, comprising:

• a. providing a sample of nucleic acids comprising at least one sequence of interest;
• b. contacting the sample of nucleic acids with a plurality of first polymerase chain reaction (PCR) primers, and a polymerase under conditions that allow PCR to occur, thereby generating a plurality of first single-sided PCR products;
• c. contacting the plurality of first single-sided PCR products with a terminal transferase and dNTPs under conditions sufficient to transfer dNTPs to the 3′ ends of the plurality of first single-sided PCR products, thereby generating a plurality of PCR products comprising 3′ tails;
• and
• d. contacting the plurality of PCR products comprising 3′ tails with a plurality of second PCR primers, and a polymerase under conditions that allow PCR to occur;
• thereby generating a library of nucleic acids with adapters at the 5′ and 3′ ends.

A method of preparing a library of nucleic acids, comprising:

• a. providing a sample of nucleic acids comprising at least one sequence of interest;
• b. contacting the sample of nucleic acids with a terminal transferase and NTPs under conditions sufficient to transfer NTPs to the 3′ end of the nucleic acids thereby generating a plurality of nucleic acids comprising 3′ tails;
• c. contacting the plurality of nucleic acids comprising 3′ tails with a plurality of first adapters and a reverse transcriptase under conditions sufficient for first strand complementary DNA (cDNA) synthesis to occur, thereby generating a plurality of cDNAs,
• wherein the plurality of cDNAs comprise 3′ polyC sequences;
• and
• d. contacting the plurality of cDNAs with a second adapter under conditions sufficient to allow generation of double stranded DNA from the plurality of cDNAs to generate a plurality of double stranded DNAs,
• thereby preparing a library of nucleic acids with adapters at the 5′ and 3′ ends.