What does cDNA represent?

cDNA, or complementary DNA, is synthesized from messenger RNA (mRNA) through a process called reverse transcription. This process involves using the mRNA as a template to create a complementary DNA strand. Importantly, during the synthesis of cDNA, only the exons of the gene are included, as introns have already been spliced out during the processing of mRNA. Therefore, cDNA represents a copy of the mRNA that reflects the coding sequences of the gene without the non-coding introns.

The choice that states cDNA is DNA that is modified to remove introns aligns perfectly with this understanding, as cDNA serves the purpose of coding for proteins without the interruption of introns found in the original genomic DNA. This unique characteristic makes cDNA a valuable tool in molecular biology, particularly in cloning, gene expression analysis, and the production of recombinant proteins.