IGCSE Biology glossary
Ligase
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Definition
An enzyme that joins together two pieces of DNA by forming bonds between the sugar-phosphate backbones. In genetic engineering, DNA ligase is used to seal the desired gene into the plasmid vector after it has been cut by a restriction enzyme.
What to include in an exam answer
Ligase 'glues' the gene into the plasmid. It is used after the restriction enzyme has cut the DNA. Remember: restriction enzyme cuts, ligase joins.
Example in context
State the role of ligase in genetic engineering (1 mark): Ligase joins the inserted gene to the plasmid DNA by sealing the sugar-phosphate backbone, forming a recombinant plasmid.
Related syllabus topic
Biotechnology & genetic modification