title: [The effect on DNA quantification and STR typing from cigarette butts collected at various time points].
abstract: OBJECTIVE
  To explore the effect on DNA quantification and STR typing from cigarette butts collected at different time points.
  
  
  METHODS
  Forty "Hongshuangxi" brand cigarette butts smoked by ten different individuals (4 cigarettes per individual) were collected. DNA was extracted from the outer layer and the sponge of the cigarette butts using chelex-100 extraction kit, as well as STR typing and DNA quantitation were simultaneously performed in 1, 4, 7 and 10 weeks, respectively.
  
  
  RESULTS
  The DNA quantities extracted from the outer layer at the 1st, 4th, 7th and 10th week were 0.104-2.52, 0.110-2.41, 0.0960-2.32 and 0.085 0-2.28 ng/microL, while the detection rates for 16 loci by STR typing were 100%, 90%, 75% and 62.5%, respectively. The DNA quantities extracted from the sponge were 0.0180-2.40, 0.0171-2.25, 0.0165-2.15 and 0.0160-2.15 ng/microL, while the detection rates for 16 loci by STR typing were 97.5%, 82.5%, 50% and 12.5%, respectively.
  
  
  CONCLUSIONS
  There is little difference in DNA quantity between the outer layer and the sponge of butts during 10 weeks, but there is an obvious effect on STR typing with prolonged extracting time. There is a much more effect on the sponge than on the outer layer, and the longer the standing time is, the lower the detection rate is.
authors.affiliation: Department of Forensic Medicine, Zhongshan Medical College, Sun Yat-sen University, Guangzhou 510080, China. zhangaiping0721@126.com
authors.forename: Ai-Ping
authors.initials: AP
authors.lastname: Zhang
authors.forename: Xiao-Hui
authors.initials: XH
authors.lastname: Chen
authors.forename: Chang-Hui
authors.initials: CH
authors.lastname: Liu
authors.forename: Li-Wei
authors.initials: LW
authors.lastname: Chen
authors.forename: Jian-Wei
authors.initials: JW
authors.lastname: Li
authors.forename: Chao
authors.initials: C
authors.lastname: Liu
mesh_terms: D004247:DNA / Q000032:analysis*; D016172:DNA Fingerprinting / Q000379:methods*; D004847:Epithelial Cells / Q000737:chemistry*; D053803:Forensic Genetics / Q000379:methods; D006801:Humans; D018895:Microsatellite Repeats / Q000235:genetics*; D009061:Mouth Mucosa / Q000166:cytology; D012907:Smoking; D013997:Time Factors
chemical_list: D004247:DNA