Plasmids, Restriction Enzymes, and DNA Ligase
The main tools
Plasmids
A plasmid is a small circular piece of DNA found in many bacteria. Scientists use plasmids as vectors because they are easy to work with and can copy themselves inside cells.
Restriction enzymes
Restriction enzymes are proteins that cut DNA at specific sequences. They work like molecular scissors, making it possible to open a plasmid and prepare a matching DNA fragment.
DNA ligase
DNA ligase is an enzyme that joins DNA pieces together. If restriction enzymes cut the plasmid and the gene, ligase can seal the gene into the plasmid.
Matching ends
Cutting DNA and plasmids with the same restriction enzyme often creates matching ends, which makes joining easier.
Tool summary
Tools and jobs
| Tool | Job |
|---|---|
| Plasmid | Carries DNA into a cell |
| Restriction enzyme | Cuts DNA |
| DNA ligase | Joins DNA |
| Host cell | Copies DNA |
Which enzyme joins DNA pieces together?
DNA ligase seals DNA fragments into one continuous molecule.
Correct answer: DNA ligase
What is a plasmid?
Plasmids are commonly used carriers in cloning.
Correct answer: A plasmid is a small circular DNA molecule used as a vector.
Restriction enzymes are most like which tool?
They cut DNA at specific sequences, like molecular scissors.
Correct answer: Scissors