Recombinant DNA
DNA made by joining pieces from different sources. A gene is cut out, joined into a plasmid (a small circle of bacterial DNA) with DNA ligase, and put into bacteria, which copy it and make the protein.
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Analogy
Pasting a recipe into a cookbook that a factory already follows.
In practice
Human insulin is made by bacteria carrying the human insulin gene on a plasmid.
Practice
Flashcards
- What is a plasmid used for in cloning?It carries the foreign gene into bacteria, which then copy it.
- Which enzyme joins DNA pieces together in cloning?DNA ligase.
Interview questions
- Describe the steps of producing human insulin in bacteria using recombinant DNA.
- Cut gene and plasmid with same restriction enzyme
- Join with DNA ligase
- Insert plasmid into bacteria
- Bacteria multiply and express the gene
- Collect and purify the protein
Questions people ask
What is a plasmid?
A plasmid is a small circular piece of DNA found in bacteria, separate from the main chromosome. It copies itself independently and often carries useful genes, such as antibiotic resistance. Scientists use plasmids as vehicles, called vectors, to carry foreign genes into bacteria.
How do scientists tell which bacteria took up the plasmid?
Plasmids used in cloning carry a marker, often an antibiotic resistance gene. After the plasmid is introduced, the bacteria are grown on a plate containing that antibiotic. Only cells that took up the plasmid survive and form colonies, so those are the ones to keep.