Amount of DNA in forensic cases is often small and sometimes degraded making

Amount of dna in forensic cases is often small and

This preview shows page 68 - 72 out of 98 pages.

Amount of DNA in forensic cases is often small and sometimes degraded, making VNTR analysis difficult V. Short Tandem Repeats (STRs) Similar to VNTRs, but shorter (less than 10 nucleotides long) o Also known as microsatellites or microsatellite DNA o Inherited from parents General process: o DNA sequences amplified by PCR PCR primers tagged with fluorescent dyes o PCR products separated by polyacrylamide gel electrophoresis o Gel analyzed for size and fluorescence of DNA STRs o Can also be analyzed using capillary electrophoresis o A match is made by comparing profiles Advantages: o STRs are more efficiently amplified by PCR o STR analysis may still yield information from less-than-optimal specimens More useful in forensics o Requires less specimen and can be performed in 24-48 hours Image:
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67 VI. Combined DNA Index System (CODIS) Federally maintained database of DNA obtained from o Crime scenes o Convicted violent offenders FBI adopted 13 “core” STR loci on various chro mosomes o Also analyzes amelogenin locus Determines gender X & Y chromosome have different size PCR products Database used to look for potential matches between DNA from crime scenes & suspects Image: City Tech OpenLab
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68 Homework: DNA Fingerprinting Complete the questions based on the virtual animations then complete the corresponding assignment in Blackboard. Part 1: DNA Fingerprinting for Human Identification Website: Human Identification Family 1. In what country did the first practical test of DNA fingerprinting occur? 2. What type of case was this first use of DNA fingerprinting? 3. What kind of tandem repeats did Alec Jeffreys study? 4. How did Jeffreys create DNA fragments for analysis? 5. What type of blotting technique was used by Jeffreys? 6. Jeffreys’ DNA fingerprinting method is known as _______________ fingerprinting. Part 2: DNA Fingerprinting & The Innocence Project Website: Human Identification Innocence 7. What type of markers were used to prove the innocence of Marvin Lamont Anderson? 8. Are STRs are located in the coding or non-coding region of the chromosome? 9. In the PCR described in this exercise, how are the primers labeled? 10. Name the three loci labeled with the yellow fluorescent dye. 11. The polyacrylamide gel used to separate amplified DNA fragments can distinguish alleles that differ in how many nucleotides? 12. The probability of a specific STR profile occurring randomly in a population is known as _____________________.
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69 Lecture 12: Exam 2 Review Complete this study guide to review for Exam 2. Be sure to review material from Exam 1 also. 1. What does “PCR” stand for? 2. What are the main components in PCR reactions? Can you label these components? What is the function of each?
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