define the term recombinant DNA

Principles of Genetic Technology

Recombinant DNA

Recombinant DNA (rDNA) is DNA that has been artificially created by combining genetic material from two or more different sources. Think of it as a new recipe made by mixing ingredients from different cookbooks. DNA is a polymer of nucleotides: $A, T, C, G$.

🧬 Analogy: Imagine you have a recipe for chocolate cake (human gene) and a recipe for quick bread (bacterial plasmid). You cut a piece of the chocolate cake recipe and paste it into the quick bread recipe. The result is a new dish that contains parts of both original recipes. In biology, this new dish is recombinant DNA.

🔬 Example: Scientists isolate the human insulin gene and insert it into a plasmid that can be taken up by E. coli bacteria. The bacteria then produce human insulin, which can be harvested for medical use.

The process of cutting DNA with restriction enzymes can be represented as:

$$\text{Restriction enzyme} + \text{DNA} \rightarrow \text{DNA fragments}$$

• Uses restriction enzymes to cut DNA at specific sequences.
• Ligase enzyme joins the cut DNA fragments together.
• Resulting plasmid can replicate inside a host cell.
• Allows production of proteins, gene therapy, and more.

Exam Tip: When answering questions about recombinant DNA, remember to mention the key enzymes (restriction enzymes, ligase) and the steps (cutting, joining, transformation). Use the analogy of cutting and pasting to explain the concept simply. Also, be ready to discuss applications such as insulin production, gene therapy, and GM crops.