Type II Restriction Endonuclease
Definition
A bacterial enzyme that cleaves double-stranded DNA at a specific palindromic recognition sequence, generating fragments whose ends reflect the exact geometry of the cut site (sticky or blunt). The class most useful in molecular biology and forensic applications.
- Recognition site
- Specific palindromic sequence
- Cut geometry
- Fixed, sequence-defined position
- Products
- Sticky or blunt ends
- Use
- Preferred class for cloning and molecular biology
Common questions
Why is Type II preferred over Type I restriction enzymes in cloning and forensic molecular work?+
Type I enzymes cleave DNA at a distance from their recognition site and produce variable, unpredictable fragment ends, while Type II enzymes cut at a fixed position within or near the recognition sequence, giving reproducible fragments that ligate predictably.
What does a sticky end allow that a blunt end does not?+
A sticky end leaves a short single-stranded overhang that can base-pair with a complementary overhang from another fragment cut by the same or a compatible enzyme, which makes directional ligation into a vector far more efficient than blunt-end ligation.
Related terms
- Bacterial Artificial Chromosome (BAC)
- An F-plasmid-derived cloning vector capable of carrying 100-300 kb inserts stably in E. coli at one copy per cell. The Human Genome...
- Blue-White Screening (Alpha-Complementation)
- A colony selection method for pUC-family vectors in which intact lacZ-alpha produces functional beta-galactosidase that cleaves X-gal to a blue indigo product....
- Multiple Cloning Site (MCS)
- A short stretch of synthetic DNA containing a cluster of unique restriction sites, engineered into cloning vectors such as pUC19 and pBlueScript...
- Plasmid
- A small, circular, double-stranded DNA molecule that replicates autonomously inside a bacterial cell. Used as a cloning vector when equipped with a...
- RFLP (Restriction Fragment Length Polymorphism)
- The first DNA profiling method used in forensic casework, developed by Alec Jeffreys in 1984. Restriction enzymes cut DNA at specific sequences,...
- Sticky End (Cohesive End)
- A single-stranded overhang generated when two cuts on opposite strands of a DNA duplex are offset rather than directly opposite each other....