DNA Review Packet S Q 14 What was

DNA Review Packet S

Q 14. What was the dominant DNA typing procedure in the US until the mid-1990 s? S RFLP analysis

Q 15. What is a short tandem repeat (STR)? Why are STRs so attractive to forensic scientists? S A STR is a region of a DNA molecule that contains short segments consisting of three to seven repeating base pairs. S STRs are attractive to FS because hundreds of different types of STRs are found in human genes. The more STRs one can characterize, the smaller the percentage of the population from which these STRs can come, thus making it easier to positively link biological evidence with a particular suspect. Also, STRs can be replicated by PCR.

Q. 16 How does the number of STRs characterized relate to the frequency of occurrence of the analyzed sample in the general population? S The greater the number of STRs characterized, the smaller the frequency of occurrence of the analyzed sample in the general population.

Q 18. What gene is often used to determine the sex of a DNA contributor? What characteristic of the gene allows forensic scientists to make this determination? S Oops! You can skip this one, too. S You know what? You deserve a sticker. See Ms. Bloedorn and keep up the good work.

Q 19. List two differences between nuclear DNA and mitochondrial DNA. S Nuclear DNA is found in the nucleus and inherited from both parents. S Mitochondrial DNA is found outside the nucleus in the mitochondria and inherited from the mother.

Q 20. Name one advantage and three disadvantages of mt. DNA analysis compared to nuclear DNA profiling. S One advantage is it is significantly more sensitive than nuclear DNA profiling. S Disadvantages: S More time consuming S More costly S Has far less discriminating power than STRs

Q 21. What is CODIS? How is CODIS useful to forensic scientists? S CODIS (Combined DNA Index System) is a computer software program developed by the FBI that maintains local, state, and national databases of DNA profiles from convicted offenders, unsolvedcrime scene evidence, and profiles of missing people. S CODIS is useful to FS because it allows them to compare DNA types recovered from crime scene evidence to those of convicted sex offenders and criminals.

Q 23. What type of gloves should an evidence collector wear when handling biological evidence? Name two reasons he or she should wear this type of glove. S An evidence collector should wear latex gloves because: S 1) Biological evidence should be assumed to be infectious. S 2) It reduces the possibility of contamination.

Q 24. What type of packaging should not be used for biological evidence? Why? What should be used? S Plastic or air-tight packaging should not be used for biological evidence, because the moisture could let bacteria and fungi grow, which can destroy DNA. S Evidence should be packaged in a paper bag or well- ventilated box.

Q 25. How should packages containing biological evidence be stored until they are delivered to a lab? S They should be refrigerated or stored in a cool location until they can be delivered.

Q 27. Name and describe the least intrusive method for obtaining a DNA standard/reference. S A buccal swab (a swab of the inside of a cheek) is the least intrusive method for obtaining a DNA standard.

Q 29. List the sequence of bases… S GCTTAGCGTTAGCTGGAC

Q 30 S Test for Y-STRs, following the same procedure as any other STR test.