Forensic Biology by Richard Li

1. Chapter 10: Blood Group Typing and Protein Profiling Forensic Biologyby Richard Li

2. Blood Groups • Antigen polymorphisms that are present on the erythrocyte surface • 29 blood group systems • E.g. Rh, MNSs, Kell, ABO • ABO system is the most commonly used in forensics Forensic Biology by Richard Li

3. Blood Groups • ABO System • A, B, AB, O • Type A: have A antigen • Type B: have B antigen • Type AB: both A and B antigens • Type O: neither A nor B antigens • Found in many tissues other than blood Forensic Biology by Richard Li

4. Biosynthesis of Antigens • O Antigen (H antigen): generated by all • Fucosyltransferase • Galactosyltransferase Forensic Biology by Richard Li

5. Secretors vs. Nonsecretors • Secretors • A, B, O antigens are widely distributed in other tissues • Approx. 75% of Caucasians • Nonsecretors • Homozygous for a nonsense mutation in FUT2 resulting in a truncated protein • Approx. 20% of Caucasians Forensic Biology by Richard Li

6. Forensic Applications • Individuals divided into four groups • Probability of two randomly chosen individuals will be identical for a known blood type is high • Can exclude suspects Forensic Biology by Richard Li

7. Techniques for Blood Group Typing • Agglutination Assays • Lattes Crust Assay • Absorption-Elution Assay Forensic Biology by Richard Li

8. Forensic Protein Profiling • Developed due to limitations with blood group typing • Inherited protein polymorphic markers • 20-30% of proteins in humans are polymorphic • Identification: • Electrophoretic separation based on molecular weight and the charge of the protein variants Forensic Biology by Richard Li

9. Hemoglobin • More than 200 Hb variants identified • Useful markers • Fetal Hb • E.g. Infanticide • Hemoglobin S • Investigative leads for indication of ethnic origin Forensic Biology by Richard Li