1. Forensic Serology

2. Blood l A complex mixture of cells, enzymes, proteins & inorganic substances l Fluid portion of blood is called the plasma (55% of blood content) –primarily water –red cells (erythrocytes) –white cells (leukocytes) –platelets

3. Searching for Blood l Tests are based on reducing capacity of hemoglobin in blood l Kastle-Meyer test –Phenolphthalein turns pink in presence of blood and H 2 O 2 l Luminol –Glows when mixed with blood

4. Erythrocytes l Transport oxygen from the lungs to the body tissues l Transport carbon dioxide from the tissues to the lungs l Red blood cells possess chemical structures on their surfaces called antigens or agglutinogens l impart blood type characteristics

5. Antibodies or Agglutinins Antibodies or Agglutinins l Types of proteins that are present in the serum l responsible for ensuring that the only blood cells that can survive in a person are cells of the correct blood type l Antibodies produced by the A alleles remove any red blood cells containing B antigens by clumping them together l Antibodies produced by the B alleles remove any red blood cells possessing A antigens

6. Blood Type l Three types (alleles) of blood type gene –A, B, O l Each individual inherits one blood type gene from their mother & one from their father l 6 possible combinations (genotypes) l AA, BB, OO, AB, AO, and BO l Genotype determines blood type

7. Type O Blood l Possessed by people whose genotype is OO –both parents passed on the O gene l have no antigens l these cells can be introduced into a person with Type A or Type B because these cells are not attacked by the antibodies these people possess l have both a & b antibodies l can only have other O type cells mixed with this blood

8. Type A l Possessed by people with genotype –AA –AO l A is dominant to O l Possesses antibody b l will destroy any Type B red cells l compatible with A or O red cells

9. Type B l Possessed by people with genotype –BB –BO l B is dominant to O l Possesses antibody a l will destroy any Type A red cells l compatible with B or O red cells

10. Type AB l Possessed by people with genotype –AB –A & B are co-dominant l Possesses no antibody l can have A, B, AB, or O cells added l Can’t be added to any other blood type without being destroyed by an antibody

11. Blood Typing l Blood typing is done by reacting whole blood with antibody A and antibody B l Antibody A will cause A and AB blood to clot l Antibody B will cause B and AB blood to clot l Type O blood contains not antigens so will not clot

13. Precipitin test l Test which determines whether blood is human or not l Like immunoassay for drugs except for human blood

14. Testing for semen samples l Acid phosphatase test –Enzyme found in seminal fluid –Moist filter paper is rubbed over garment and treated with reagents l Purple color means positive for semen l MUP reagent - UV florescent l PSA -prostate specific antigen test –Immunoassay for protein found only in seminal plasma

15. Secretors vs. Nonsecretors l Secretors have A and B antigens in non- blood fluid –80% of population l Nonsecretors don’t have blood type antigens in saliva, semen, etc. –Remaining 20% of population

16. DNA evidence

17. Chromosomes l l Cells contains all the genetic info the cell needs to exist & to reproduce l l In most types of cells, genetic information is organized into structures called chromosomes l l usually X shaped – –Males have XY, females XX l l 23 pairs in humans – –one copy from mother & one from father l l Each chromosome is a single polymeric molecule of DNA l l if fully extended the molecule would be about 1.7 meters long

18. Genes l l Each chromosome contains hundreds to thousands information blocks called genes l l Each gene is the blueprint for a specific type of protein in the body l l only identical twins will have all identical genes

20. Functions of DNA l l To transmit information from one generation of cells to the next – – Replication: the synthesis of new DNA form existing DNA l l To provide the information for the synthesis of components (proteins) necessary for cellular function l l Nuclear vs. mitochondrial – –Nuclear contains all genes and is linear – –Mitochondrial contains only genes inherited from mother and is circular

21. DNA structure

22. Nitrogenous Bases

23. DNA Fingerprinting l l Sequencing: a procedure used to determine the order of the base pairs that comprise DNA l l The basic structure of everyone’s DNA is the same l l the difference between people is the ordering of the base pairs l l Every person can be distinguished by the sequence of their base pairs l l millions of base pairs make this impractical l l a shorter method uses repeating patterns that are present in DNA

24. Short Tandem Repeats l l DNA strands contain information which directs an organism’s development called exons l l Also contain stretches which appear to provide no relevant genetic information called introns – –repeated sequences of base pairs – –“junk” DNA – –30% of genome l l All humans have some tandem repeats l l Repeats come from the genetic information donated by parents

25. STR Analysis l l Usually an individual will inherit a different variant of the repeated sequence from each parent l l Restriction enzymes can cut of the sequence of repeats l l Number of repeats can be determined by electrophoresis – –More repeats: higher MW: moves less – –Fewer repeats: lower MW; Moves farther l l Example: TH01 – –A-A-T-G – –From 5 to 11 copies

27. CODIS l Combined DNA Index System l National database l 13 STR’s l Population genetics and product rule allow use to determine likelihood of finding another individual with same genetic profile