cDNA library

Definition

A collection of cloned complementary DNA (cDNA) fragments representing the expressed genes (transcriptome) of an organism or tissue, generated by reverse transcription of mature mRNA and inserted into host vectors for storage and screening. Unlike genomic DNA libraries, cDNA libraries lack introns, regulatory elements, and non-coding sequences, making them useful for isolating protein-coding sequences and studying gene expression under specific conditions.

Etymology

cDNA: complementary DNA, synthesized from an RNA template by reverse transcriptase; library: collective storage of cloned fragments

Example

An entomologist constructing a cDNA library from antennal tissue of the moth Heliothis virescens to identify odorant-binding proteins and chemosensory receptors involved in pheromone detection.

Synonyms

• expression library
• transcript library

Related Terms

• genomic library
• transcriptome
• reverse transcriptase
• EST (expressed sequence tag)
• RNA-seq
• Gene expression
• Intron
• exon

Usage Notes

Contrast with genomic DNA library: cDNA libraries capture only transcribed sequences, omitting regulatory regions and introns, and reflect tissue-specific or condition-specific expression rather than the full genetic complement. Particularly valuable in arthropod research for studying stage-specific or environmentally induced gene expression (e.g., diapause, immune response, pesticide resistance) without sequencing entire genomes. Quality depends on mRNA integrity and completeness of reverse transcription; normalization may be needed to avoid overrepresentation of abundant transcripts like ribosomal proteins.