Used to introduce recombinant dna into eukaryotic cells. Dna for preparing large quantities of a particular gene/other dna sequence. Any specific target segment within one or many dna molecules can be quickly amplified (copied many times( in a test tube). Studying the sequence, expression, & function of a gene to determine role of gene. This technique uses gel made of a polymer to acts a molecular sieve to separate nucleic acids or proteins on the basis of size, electrical charge, & other physical properties. When snp(single nucleotide polymorphism) alter the sequence recognized by a restriction enzyme change the lengths of the restriction fragments formed by digestion with that enzyme. This can occur in coding and non coding regions and is called restriction length enzyme polymorphism*rflp. They can serve as useful genetic markers, it isn"t nessacary to actually sequence the dna of multiple individuals to find.