jiafm, 2010-32(2) april-june. - forensic medicine

ISSN 0971-0973 J Indian Acad Forensic Med, 32(2)Original Research PaperDecay in Intact DNA Recovery in Blood Samples kept at RoomTemperature*Sabri Imran, **Usmani J.A., ***Hanif S.A.,****Khan A.U.AbstractBlood Samples were kept at room temperature for a period of 3-6 months at room temperature to know theamount of quantitative DeoxyriboNucleic Acid [DNA] recovery from these samples. We are able to recover goodamount of DNA for about first 3-6 weeks after which the DNA is decreased drastically and after two months therehardly any chance of intact DNA recovery from these samples. It has been concluded that blood samples recoveredfrom scene of crime after about 1-2 months is a waste. The samples must be recovered as early as possible torecover intact DNA from them. The samples must be collected within 1-2 months from scene of crime until andunless the climate is cold enough to increases decay time. This study is very useful for the investigating authoritieswhich can make errors while collecting blood samples for DNA analysis.Key Words-Blood Sample, DNA, Scene of CrimeIntroduction:Blood is the most important and mostcommon Forensic Sample recovered from the sceneof crime however the time of recovery may differfrom fresh blood to many months. Most of the timeblood was sent to the Forensic Laboratory for DNAisolation and the investigation agencies thought that itis a minor work to do, which is not so. Our study isbased on the fact that the DNA yield decreases withtime [1] but what is that time period after which weare unable to isolate the intact DNA from thesesamples.Although there is no hard and fast rule thatthis is the time after which we are unable to recoverintact DNA from the samples but our study just showchances of recovery. In the first phase of our studywe took only one type of sample [liquid blood] so asto avoid any confusion. In normal conditions blood isfound in various states like dried blood, clottedblood, liquid blood etc.Corresponding Author:Dr.Imran Sabri*Assistant ProfessorDepartment of Forensic Medicine,Dr Rajendra Prasad Govt. Medical College, TandaKangra, H.P.E-mail imransabri@gmail.comCell +919805788755, 987830036** Professor & ***Associate Professor,Department of Forensic Medicine,J.N. Medical College, AMU Aligarh*** Interdisciplinary Biotechnology Unit, A.M.U.AligarhBut only liquid blood is taken so as to guidethe investigating agencies about the chances ofrecovery of intact DNA from blood samples. A totalof sixteen samples were taken to study.Material and Methods:The Blood samples were obtained fromblood bank of J.N. Medical College Hospital wherethey were stored at 4 Centigrade Positive [3]. ZeroTime was the time when the first recovery was donewhich was same or different from time of Samplecollection from the subject or scene of crime. Beforethis time the time was be calculated as negative valuei.e.: minus one hour or minus one day etc. 2.5 ml ofblood was taken to isolate the DNA. After storage, itwas processed for DNA analysis using phenolextraction method [2]. The optical density of isolatedDNA was done by spectrophotometer.Volume of Blood Taken: 2.5 mlConc. of DNA (µg/ml) = OD260 X 50µg/ml XDilution Factor X Total Vol. in mlFormula: OD260 x conversion factor = µg/ml ofnucleic acidOD260 Unit = 50µg/ml for dsDNAConc. = Concentration OD = Optical DensityNm = Nano-Meter 50 = constantDilution Factor (Note: This is a ratio hence do nothave unit) = Amount of water or buffer used fordilution / Amount of Sample (Isolated DNAdissolved in TE Buffer ).Observations and Discussion:The yield of DNA decreases with time aslysis of DNA occurs in the samples as a result ofenzymatic action so the amount of recovery isexpected to be decreased with time. The question142