الفهرس 
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Abstract
In the last decades, many advances in molecular biology techniques had been made, including the area of forensic DNA analysis. The ability to retrieve genetic information from the contents of just few cells had made DNA profiling as one of the most relied test in forensic medicine.
DNA testing technique is so sensitive that, biological evidence too small to be easily seen with the naked eye, can be used to link suspects to crime scenes. Evidence must be carefully collected, preserved, stored, and transported prior to any analysis conducted in a forensic DNA laboratory.
The aim of the current study is to evaluate the effects of different environmental factors on recovery of DNA from blood and seminal stains spotted on cotton fabrics. These factors include; different grades of temperature (100°c, 50°c, 37°c, 4°c, -20°c and burn) different period of aging of the stain (one month, three months and six months) and different PH (acidic by concentrated sulfuric acid (98%) and alkaline by concentrated potassium hydroxide (99%)).
The present study is an experimental one conducted on twenty male volunteers, all of them were patients in Andrology clinics, Assiut University Hospitals. Their age ranged from 20 to 40 years old. Two types of samples were taken from them; (12 ml of blood and 6 ml of semen) after taken informed consent.
Macroscopic changes of the samples were noticed. This is followed by presumptive tests by using phenolphthalein test for bloodstain samples and Florence test for seminal stain samples. After that, DNA analysis for all stains was done (extraction, PCR, determination of concentration and gel electrophoresis).
The present research showed that bloodstains exposed to temperature grades 100°c and 50°c and bloodstains left for one, three and six months before processing became darker in colour while bloodstains exposed to temperature grades 37°c, 4°c and -20°c showed no colour change in comparison to the control. Burnt bloodstains became charred and black in colour. Bloodstains exposed to concentrated sulfuric acid (98%) became dark in colour and the piece of cloth had been eaten up completely after 30 min. of exposure to the acid. Bloodstains exposed to concentrated potassium hydroxide (99%) became darker in colour than the control without eating up of the piece of the cloth.
Blood could be identified in the bloodstains by phenolphthalein test after exposure to temperature grades 100°c, 50°c, 37°c, 4°c and -20°c. Blood can be identified in bloodstains left for one, three and six months before processing and also bloodstains exposed to concentrated sulfuric acid (98%) and concentrated potassium hydroxide (99%).
DNA concentration was significantly reduced in bloodstains exposed to temperature 100°c and 50°c, bloodstains left for one, three and six months before processing, bloodstains exposed to concentrated sulfuric acid (98%) and concentrated potassium hydroxide (99%) compared to the control.
DNA quality of bloodstains was not affected by temperature grades 100°c, 50°c, 37°c, 4°c and -20°c and DNA fragments could be detected by gel electrophoresis. The quality of DNA did not significantly affected by storage duration except for bloodstains left for 6 months by using Amelogenin primer.
DNA quality was affected in bloodstains exposed to concentrated sulphuric acid (98%) with using either TH01 or Amelogenin primers by gel electrophoresis and DNA fragments could not be identified. However, DNA quality did not significantly affected by exposure to concentrated potassium hydroxide (99%).
The macroscopic image of the seminal stains showed that seminal stains exposed to temperature grades 100˚c, 50˚c, 37˚c,4˚c and -20˚c appear grayish white in colour the same as the control stain. Burnt seminal stains became charred. The colour of seminal stains left for one, three and six months before processing became deep yellow compared with the control. Seminal stains exposed to concentrated sulfuric acid (98%) became dark in colour and the piece of cloth had been eaten up. Seminal stains exposed to concentrated potassium hydroxide (99%) showed that the colour of the stain became darker in colour than the control without eating up of the piece of the cloth.
Regarding the presumptive test for identification of seminal stain, seminal stains can be identified by Florence test after exposure to temperature grades 37˚c,4˚c and -20˚c and for seminal stains left for one, three and six months before processing but can not be identified in samples exposed to temperature grades 100˚c, 50˚c, the burnt samples and those exposed to concentrated sulfuric acid (98%) and concentrated potassium hydroxide (99%).
The amount of recovered DNA from seminal stains was significantly reduced in samples exposed to temperature grades 100°c, 50°c and burnt sample. Concentration was significantly reduced in seminal stains left for one, three and six months before processing and samples exposed to concentrated sulfuric acid (98%) and concentrated potassium hydroxide (99%).
DNA quality in seminal stains did not significantly affected by temperature grades 100°c, 50°c, 37°c,4°c and -20°c and DNA fragments could be detected by gel electrophoresis.
The quality of DNAwas not affected by storage duration and DNA fragments could be identified.
DNA quality was affected for seminal stains exposed to concentrated sulfuric acid (98%) by using either TH01 or Amelogenin primers by gel electrophoresis and DNA fragments could not be identified. However, DNA quality was not affected by exposure to concentrated potassium hydroxide (99%) by TH01 and DNA fragments could be detected by gel electrophoresis but not by use of Amelogenin primer.
Conclusion:
Environmental factors are considered as risk factors for stains analysis. It can lead to misinterpretation of blood or seminal stains and so misleading for the assailant in the crime.
Regarding the positive control stains; concentration of DNA recovered from seminal stains is greater than the concentration of DNA recovered from bloodstains.
Different factors affected the stains by different degrees;
As regard temperature, low temperature caused no significant decrease in DNA conc. while high temperature affected the macroscopic appearance of blood stains, caused negative results with Florence test and significant decrease in the conc. of DNA recovered from both blood and seminal stains.Burn affected all tests in both types of samples.
Regarding aging; macroscopic appearance of both samples was affected with significant decrease in their DNA concentration. DNA fragments can be detected by gel electrophoresis except for bloodstains left for six months by using Amelogenin primer.
Regarding different PH; macroscopic appearance of both samples was affected with significant decrease in their DNA concentration. DNA fragments can be detected only by TH01 primer for stains exposed to Potassium hydroxide (99%).
Results showed that TH01 is more resistant to the effect of aging as Amelogenin primer can not detect DNA in bloodstains left for six months before processing. TH01 is more resistant to the effect of different PH.