Question

A major advantage of a cDNA library over a genomic library is that cDNA

• A. Contains introns
• B. Represents non-coding regions
• C. Contains only expressed genes
• D. Is identical in all tissues

Hint:

Comparison of libraries: \[ \boxed{ \begin{aligned} \text{Genomic library} &\rightarrow \text{Entire genome} \text{cDNA library} &\rightarrow \text{Only expressed genes (no introns)} \end{aligned} } \]

Answer 1

The Correct Option is C

Step 1: Recall the origin of a cDNA library. A cDNA library is prepared from mature mRNA using the enzyme reverse transcriptase. Since mature mRNA has already undergone splicing, cDNA contains only expressed genes without introns.

Step 2: Compare with a genomic library. A genomic library contains the entire genome, including coding regions, introns, promoters and intergenic sequences. Thus, the major advantage of a cDNA library is that it \[ \boxed{\text{contains only expressed genes}.} \] Therefore, \[ \boxed{(C)} \] is the correct answer.