Detection and Evaluation of Non-Recombinants in cDNA Libraries by Multiple Cloning Region PCR

• Published in: BioTechniques Vol. 32; no. 1; pp. 88 - 92
• Main Authors: Bandyopadhyay, Dilip, Vesuna, Farhad D
• Format: Journal Article
• Language: English
• Published: Natick, MA Future Science Ltd 01.01.2002; Eaton; Taylor & Francis Group
• Subjects: Base Sequence; Biological and medical sciences; Biotechnology; Cloning, Molecular - methods; DNA Primers; DNA, Complementary; Evaluation Studies as Topic; Fundamental and applied biological sciences. Psychology; Genetic engineering; Genetic technics; In vitro gene amplification. Pcr technique; Methods. Procedures. Technologies; Molecular and cellular biology; Plasmids; Polymerase Chain Reaction - methods; Recombination, Genetic; Evaluation; Multiple; Variable; Selection; Biology; Virus; Polymerase chain reaction; Complementary DNA; Proportion; Recombinant protein; Molecular cloning; Detection; Species; Phage
• ISSN: 0736-6205; 1940-9818
• DOI: 10.2144/02321st05

Bacteriophages that are routinely used in cDNA libraries do not require any biological selection for forming plaques. Thus parental non-recombinant phages are always found in variable proportions together with recombinant ones in all cDNA libraries. The presence of non-recombinants in significant proportions dilutes the abundance of rare cDNA species and makes library screening difficult. If the exact proportion of non-recombinants in a library were known, then one would screen proportionately more plaques to get a positive clone. In the absence of such information, screening is conventionally conducted on a number that is based on the titer of the library. We have devised a method using the flanking sequences from either side of the multiple cloning region (MCR) of all λ phage vector derivatives as primers for PCR amplification. A non-recombinant phage produces a fragment equal to the size of the MCR, whereas a recombinant phage produces a fragment larger than the MCR, which is an MCR+ fragment. All cDNA libraries that we have studied show the presence of the MCR fragment (indicating non-recombinants) at variable proportions ranging between 6% and 36% of the total phages present. We also show that their presence negatively influences the retrieval of target cDNA sequences.