A researcher constructs a cDNA library from human liver mRNA and a genomic library from liver nuclear DNA. Which statement correctly distinguishes the two libraries?
- A The cDNA library contains introns and regulatory sequences, whereas the genomic library does not
- B Both libraries contain identical clones because both derive from the same tissue
- C The cDNA library represents only genes expressed in liver, whereas the genomic library contains all sequences regardless of expression ✓
- D The genomic library can be made only from mRNA, whereas the cDNA library is made from chromosomal DNA
Correct answer: C. The cDNA library represents only genes expressed in liver, whereas the genomic library contains all sequences regardless of expression
Explanation
cDNA is synthesised from mature mRNA by reverse transcriptase, so it reflects only the transcripts present in liver and lacks introns and promoter regions. A genomic library is prepared by cloning restriction fragments of total cellular DNA, so it includes introns, exons, promoters and non-expressed regions from every chromosome. Option A states the relationship backwards. Option D swaps the starting material for each library type.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.