NOTES 13.4 DNA Collection

CODIS Combined DNA Index System contains DNA profiles from convicted offenders, unsolved crime scene evidence and profiles of missing persons CODIS contains 13 STR entries – read page 390

Collection & Preservation of Biological Evidence for DNA analysis Sensitivity levels at 250 picograms – 7 picograms of DNA per cell need only 36 DNA bearing cells to obtain an STR – Refer to table 13-2 on page 390 to locate sources of DNA on pieces of evidence

What comes first? 1. Biological evidence is photographed close up 2. Location relative to crime scene is recorded in sketches and photographs 3. Blood evidence is immediate

4. Body fluids and biologically stained materials must be collected with a minimum of persona contact 5. Body fluids are considered infectious

6. Latex gloves worn 7. All clothing from victim and suspect is collected, even without the apparent presence of blood

8. Packaged in paper or box 9. Substrate control obtained 10. Materials refrigerated 11. Blood in soil must be frozen

13.4 Questions 1. What is CODIS? How is CODIS useful to forensic scientists? 2. Approximately how many DNA bearing cells are needed to obtain an STR profile? What term is used to describe a quantity of DNA that is below this normal level of detection? 3. What type of packaging should NOT be used for biological evidence? Why? 4. How should packages containing biological evidence be stored until they are delivered to a laboratory? Name one common exception and describe how it should be stored. 5. Name and describe the least intrusive method of obtaining a DNA standard/reference sample 6. List 4 ways to minimize contamination of biological evidence.