Partial restriction digestion is achieved using restriction enzymes that produce blunt or sticky ends as described below-

 i. Restriction enzymes generating blunt ends

The genomic DNA can be digested using restriction enzymes that generate blunt ends e.g. HaeIII  and AluI.

Blunt ends are converted into sticky ends prior to cloning. These blunt ended DNA fragments can be ligated to oligonucleotides that contain the recognition sequence for a restriction enzyme called linkers or possess an overhanging sticky end for cloning into particular restriction sites called adaptors.

Linkers

Linkers are short stretches of double stranded DNA of length 8-14 bp that have recognition site for restriction enzymes. Linkers are ligated to blunt end DNA by ligase enzyme. The linker ligation is more efficient as compared to blunt-end ligation of larger molecules because of the presence of high concentration of these small molecules in the reaction. The ligated DNA can be digested with appropriate restriction enzyme generating cohesive ends required for cloning in a vector. The restriction sites for the enzyme used to generate cohesive ends may be present within the target DNA fragment which may limit their use for cloning.

Adapters

These are short stretches of oligonucleotide with cohesive ends or a linker digested with restriction enzymes prior to ligation. Addition of adaptors to the ends of a DNA converts the blunt ends into cohesive ends.