The study of antigen-antibody reactions The Nature of Blood-1 Blood is a complex mixture of: Cells Enzymes Proteins Fluid Portion is called Mostly water accounts for 55% of blood Cells Suspended in Plasma Erythrocytes (Red Blood Cells) Leukocytes (White Blood Cells) Platelets Plasma The Nature of Blood-2 Antigens and Antibodies RBCs transport O 2 from the lungs to body tissues May have antigens on surface Antigens are grouped into the ABO and Rh systems. Type A-has A antigens on its surface Type B-has B antigens on its surface Type AB-contain both A and B antigens on its surface Type O-has neither antigens on its surface The Nature of Blood-3 Antigens and Antibodies cont. Rh Factor- person can be Rh+ or Rh- Rh+: has D antigen on its surface Rh-: does not have D antigen on its surface For every antigen there is an antibody Anti-A Anti-B Anti-D Antibodies only react with its specific antigen and no other. See Figure 8-1 pg 270 (Draw, color, and label) The Nature of Blood-4 Antigens and Antibodies cont. Blood TypeAntigen on RBCAntibodies AAAnti-B BBAnti-A AB Neither O Both The Nature of Blood-5 Blood Typing Blood typing is accomplished by using 2 serums: Anti- A and Anti-B Distribution of Blood Types in the US OABAB 43%42%12%3% Forensic Characterization of Bloodstains-1 The science of bloodstain analysis somewhat traditionally follows certain steps which serve to adequately describe the various tests conducted. Those steps are: 1. Is the sample blood? 2. Is the sample animal blood? 3. If animal blood, from what species? 4. If human blood, what type? 5. Can the sex, age, and race of the source of blood be determined? Miller vs. Pate Miller vs. Pate (1967) Forensic Characterization of Bloodstains-2 Color Tests Benzidine test- used in the past, but has been identified as a carcinogen Kastle Meyer test-turns a deep pink in the prescence of blood due to rxn b/w blood, phenolphthalein, and H2O2. Hemastix test-field test that when moistened with distilled H2O and placed in contact w/ blood turns green. Forensic Characterization of Bloodstains-3 Luminol Extremely sensitive test In the presence of blood, produces a light rather than a color. Produces a faint blue glow Can easily be sprayed over large areas Does NOT interfere w/ any subsequent DNA testing Forensic Characterization of Bloodstains-4 Microcrystalline Tests Makes ID of blood more specific. Depends on addition of chemicals to produce crystals Less sensitive than color tests and susceptible to contaminants. Two most popular tests: Takayama and Teichmann Forensic Characterization of Bloodstains-5 Precipitin Test Antibody-antigen reaction forms a precipitate. Helps distinguish if blood is from human or of other animal origin. Based on the fact that when human blood is injected into a rabbit antibodies form to neutralize its presence. The animal is bled and the blood serum is isolated and is known as human antiserum. Forensic Characterization of Bloodstains-6 Gel Diffusion Electrophoresis is used to move antigens and antibodies towards each other. The extracted bloodstain and human antiserum are place in separate holes opposite each other on the gel. If the blood is human, a line of precipitation forms where the antigens and antibodies meet. Immunoassay Techniques-1 Produces antibodies that reacting with drugs A specific drug and protein are combined and injected into an animal (rabbit or mouse). Drug-protein complex acts as an antigen stimulating the animal to produce antibodies. The recovered blood serum form the animal now contains antibodies specific to the drug. Immunoassay Techniques-2 Types RIA (Radioimmunoassay)- Drugs are labeled w/ radioactive tags There are questions about the reliability of RIA EMIT (Enzyme-Multiplied Immunoassay Technique)- Drugs are labeled w/ an enzyme tag Adding urine antibodies that bind to a type of drug being looked for. A chemically labeled version of the drug is added. Competition between the labeled and unlabeled to bind w/ the antibody occurs-signifies urine screen test is positive. Bloodstain Patterns-1 Useful in reconstructing the events that produce bleeding. Analysis of bloodstain patterns is extremely complex. Interpretation of bloodstain patterns necessitates carefully planned control experiments using surface materials comparable to those found at the crime scene. Bloodstain Patterns-2 Important observations and conclusions to be considered. Bloodstain Patterns-3 Principles of Heredity-1 Genes and Chromosomes Hereditary material is transmitted by a molecule called DNA that is composed of genes. Genes control the development and growth of every body structure. DNA tightly coils into structures called chromosomes. Chromosomes are found in the nucleus of every cell. All body cells in a human have 46 chromosomes (23 pairs) 2 of the 46 determine gender. Sex cells (egg or sperm) have 23 chromosomes. Fertilization Occurs when a sperm and egg combine Girl=XX Boy=XY Principles of Heredity-2 Genes and Chromosomes Alleles Alternative forms of a gene. Ex: Blood Type (controlled by 3 genes A,B and O) Combinations: AA=homozygous dominant for type A blood AO=heterozygous for type A blood BB=homozygous dominant for type B blood BO=heterozygous for type B blood AB=heterozygous for type AB blood OO=homozygous recessive for type O blood Principles of Heredity-3 Genes and Chromosomes Genotypes and Phenotypes Genotype-genetic makeup of an individual (the letters) Phenotype-physical appearance as a result of the genotype (appearance) Ex: The letters AA are the genotype. The appearance as a result of the genotype is Type ____ blood. Practice Punnett Squares Father M o T h er OO A B Father MOThERMOThER OO AAO BBO Principles of Heredity-4 Paternity Testing Paternity Testing Disputed paternity can be resolved by comparing blood group genotypes of suspected parents. If a child has AB blood it is unlikely he is the father: Combined with HLA (human leukocyte antigen) test and DNA testing the odds of establishing paternity are beyond 99% OO AAO BBO Forensic Characterization of Semen-1 Testing for seminal stains Acid Phosphatase Test- Moistened filter paper is rubbed lightly over suspect areas. One or two drops of sodium alpha- naphthylphosphate and Fast Blue B dye are added to the paper. The paper will turn purple if acid phosphatase is present. Acid phosphatase is an enzyme found in semen. Secreted by the prostate gland Presence is indicated when it comes in contact with an acidic soln. of sodium alpha naphthylphosphate and Fast Blue B dye. Forensic Characterization of Semen-2 Testing for seminal stains Microscopic Examination of Semen Identified by presence of spermatozoa via microscopic examination. Spermatozoa are slender, elongated cells with a thin flagellate tail. Are usually easily located, but will bind tightly to cloth materials. Stained material can be placed in water and stirred. Spermatozoa will be present in the volume of water and some water can be extracted and dried onto a microscope slide, stained and examined under the microscope. Forensic Characterization of Semen-3 Testing for seminal stains Prostate Specific Antigen Protein that allows specific identification of semen. Unique to seminal plasma. Semen and anti-p30 are placed in wells. The antigen and antibody move toward each other. If a visible precipitation line forms it is proof the stain is seminal in nature. Collection of Rape Evidence-1 Medical examination of a rape victim must occur immediately after an assault. Outer and undergarments from those involved are carefully removed and packaged separately in paper bags. Victim is placed on a clean sheet and asked to remove clothing. All foreign material will drop on sheet. Clothing is packaged appropriately. Bedding or the object on which the assault took place should be submitted for processing. Collection of Rape Evidence-2 Items containing stains should not be folded due to flaking of the stain. Objects to large to submit to the lab should be cut and sent with a piece that does not contain a stain for a control. In the lab seminal stains are linked to a donor using DNA typing. Collection of Rape Evidence-3 Physical evidence that MUST be collected: Pubic combings Pubic hair standard/reference samples External genital dry-skin areas Vaginal swabs and smear Cervix swabs Rectal swabs and smear Oral swabs and smear Head hairs Blood sample Fingernail scrapings All clothing Urine specimen Collection of Rape Evidence-4 If suspect is apprehended the following is collected: All clothing Pubic hair combings Pulled head and pubic hair standard/reference samples Penile swab Blood sample or buccal swab