From mRNA to DNA—Identifying the Product of Reverse Transcription Which type of DNA is synthesized when processed messenger RNA (mRNA) molecules are used as templates with reverse transcriptase?

Introduction / Context:Converting mRNA into complementary DNA enables cloning and expression of protein-coding sequences without introns. This is essential for expressing eukaryotic genes in prokaryotic hosts and for transcriptome analyses.

Given Data / Assumptions:

• Template is processed mRNA (polyadenylated, introns removed).
• Enzyme is reverse transcriptase.
• Priming can use oligo-dT, random primers, or gene-specific primers.

Concept / Approach:Reverse transcriptase copies the mRNA sequence into single-stranded DNA, which is then converted to double-stranded complementary DNA (cDNA). Because the template is processed mRNA, cDNA lacks introns and often reflects only the transcribed, spliced exons and untranslated regions.

Step-by-Step Solution:

Verification / Alternative check:cDNA libraries are screened to study gene expression; expression of eukaryotic ORFs in bacteria typically uses cDNA to avoid introns that bacteria cannot splice.

Why Other Options Are Wrong:

• rDNA refers to genomic rRNA gene repeats, not reverse-transcribed products.
• mDNA/tDNA as listed are non-standard or misleading in this context.
• Genomic DNA contains introns; it is not synthesized from mRNA templates.

Common Pitfalls:Assuming cDNA equals genomic DNA; cDNA represents expressed sequences and lacks introns, making it ideal for coding-region studies.

Final Answer:cDNA