質體可能會以：纏繞程度不同的環狀、部分分裂或是線狀，以及串聯多聚體等不同構型呈現。常見的構型類別為：covalently closed circular (ccc) form, the open circular (oc) form (也稱作 “nicked form”), linear form(經過限制酶digest)
限制性片段長度多態性 Restriction Fragment Length Polymorphism (RFLP)此技術是於1984年英國科學家Alec Jeffreys在研究遺傳性疾病期間發展此技術，Jeffreys分析透過DNA序列重複之現象，證明遺傳性之關聯及個體差異，即為知名串聯重複 Variable Number of Tandem Repeats (VNTRs)，其發現此現象皆存在於所有人類身上但會因個體差異導致長度及重複的次數皆不相同。
SNP genotyping is the measurement of genetic variations of single nucleotide polymorphisms (SNPs) between members of a species. Single-nucleotide polymorphisms (SNPs) are widespread genomic variations, which are associated with serious health disorders and drug resistance.
