Forensic Serology –In 1901 Karl Landsteiner discovered that blood has different types. He won the Nobel Prize for this discovery.

We call the system he started developing the A- B-O system. Some blood types will not mix with other blood types. Before DNA analysis blood was commonly used to link a person to a crime.

I – THE NATURE OF BLOOD A.Antigens & Antibodies 1. Blood is a highly complex mixture of cells, enzymes, proteins, and inorganic substances.

2. The fluid part of blood is called plasma. Plasma is composed mostly of water and makes up 55% of blood content.

3. Suspended in the plasma are solid materials, mostly red blood cells (erythrocytes), white blood cells (leukocytes), and platelets.

Red blood cells

White blood cells

Platelets

4. The solid part of blood accounts for 45% of its content.

5. Blood clots when a protein called fibrin traps the red blood cells. After the clotted blood is removed, a pale yellowish liquid called serum is left behind.

6. Forensic scientist are mostly interested in red blood cells and serum. 7. Bloods function is to transport oxygen from the lungs to tissues and to transport CO 2 from the tissues to the lungs.

8. On the surface of each blood cell are chemical structures called antigens. These allow red blood cells to be categorized. There are more than 15 antigen systems known.

9. The A-B-O and Rh systems are the best known and most important. If an individual has type A blood they have the A antigen located on its surface.

A person with type B blood has B antigens on its surface. A person with type AB has both antigens on its surface.

A person with type O has ___ antigens on the surface of the red blood cells.

10. Another important blood antigen is designated as the Rh factor (or D antigen). People that have the D antigen are said to be Rh positive.

Those without are Rh negative. 11. Serum is important because it contains proteins known as antibodies.

The fundamental principle of blood typing is that for every antigen there exists a specific antibody. Each antibody symbol contains the prefix anti followed by the name of the antigen for which it is specific.

Anti-A is specific for A antigen, anti-B is specific for B antigen. An antibody will react only with its specific antigen and no other.

If serum containing anti B is added to red blood cells carrying B antigen the two will combine causing the antibody to attach to the blood cell.

Antibodies are bivalent, meaning they have two reactive sites, so they can attach to two cells at the same time. This causes clumping of the cells known as agglutination.

In the serum of type A blood we find anti-B and no anti-A, type B blood has anti-A but not anti-B. Type AB has what kind of antibodies?

Neither! Type O has both anti-A and anti-B.

B. Blood Typing 1. The term serology is used to describe a broad scope of lab tests that are used specific antigens and antibody reactions.

The most widely used test are used to determine the A-B-O blood type. To do this you only need anti-A and anti-B antiserums.

2. Blood type distribution in the U.S. O = 43% A = 42% B = 12% AB = 3%

II – Immunoassay Techniques A. Techniques and Concepts 1. Uses the antigen-antibody reactions, used to determine blood type, to detect drugs in the blood.

By combining the drug with a protein and injecting it into an animal the blood (serum) of that animal will contain antibodies specific for that drug.

The most common immunological assay technique is the ENZYME-MULTIPLIED IMMUNOASSAY TECHNIQUE (EMIT).

It is a quick and sensitive technique used to detect drugs in urine. Ex. A person being tested for heroin will have heroin antibodies added to the urine.

If heroin is present the antibodies will combine with the drug and result in a positive test. The amount of antigen left can be used to determine the concentration of the drug in the urine.

III Forensic Characteristics of Bloodstains. 1.The Three questions most frequently asked when examining blood are?

Is it blood? From what species did the blood originate? How closely can the blood be associated with a particular individual?

2. The Kastle-Meyer color test is used to confirm blood is blood. It combines phenolphthalein, hydrogen peroxide and the dried blood sample.

These will react with the hemoglobin in the blood to turn a deep pink color. 3. The Luminol Test is another presumptive test for blood resulting in the production of light instead of color.

By spraying the luminol reagent onto a suspect item, large areas can be screened for the presence of blood.

The area containing blood will become luminescent. The luminol test is capable of detecting bloodstains diluted up to 300,000 times. It will not interfere with DNA test that may need to be performed.

4. Once the stain has been confirmed as blood, the next step is to determine whether the stain is of human origin. The most common test is the precipitin test.

Precipitin tests are based on the fact that when animals (rabbits) are injected with human blood, antibodies are formed that react with the human blood to neutralize it.

The antibodies can be recovered by isolating the blood serum. This serum will contain antibodies that will specifically react with human antigens.

The serum is known as human antiserum. This same method can be used to make antiserum for other species.

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IV – Stain Patterns of Blood –The location, distribution, and appearance of bloodstains and spatters may be useful for interpreting and reconstructing the events that must have occurred to produce the bleeding.

The interpretation of bloodstain patterns often necessitates careful planned control experiments using surface materials similar to those found at the crime scene.

General rules- –The harder and less porous the surface the less spatter results –The pointed end of a bloodstain always faces its direction of travel.

- A drop of blood striking a surface at right angles creates a nearly circular stain; as the angle decreases, the stain becomes elongated in shape.

- The origin of a blood spatter can be determined by drawing straight lines through the axis of several individual bloodstains. The intersection or point of convergence of the lines represents the point from which the blood emanated.

V – Principles of Heredity A. Transmission of Traits 1. The transmission of hereditary material is accomplished by genes.

The gene is the basic unit of heredity. The genes determine the characteristics of an individual.

2. Genes are located on chromosomes. The chromosomes are located in the nucleus of the cell. Humans have 46 chromosomes (23 pair).

The reproductive cells, the egg and the sperm, only have ½ the number of chromosomes (23). During fertilization, 23 chromosomes from the egg unites with 23 from the sperm to total 46 for the embryo.

The new individual gets some genetic material from each parent. 3. Reproductive cells always contain an X–chromosome. This is the female chromosome. The males have a Y-chromosome.

XX = female XY = male

4. Chromosomes come in pairs. Similar genes are located on similar chromosomes. The position a gene occupies on a chromosome is its locus.

Alternate forms of genes that influence a given characteristic and are aligned with one another on a chromosome are known as alleles.

5. For blood there are 3 alleles: A, B, O. A gene made up of two of the same alleles is said to be homozygous (AA, BB, OO).

A gene pair made up of two different alleles is said to be heterozygous (AB, AO, BO). With different alleles for the same trait one will usually be dominant and the other recessive.

With the A-B-O blood group A and B are codominant while O is recessive. A person with type AO will be typed as A etc.

The recessive characteristics of O will appear only when both recessive alleles are present.

A pair of alleles together constitutes the genotype of the individual. The genotype tells us both alleles present (AO, BO). A persons phenotype is the outward expression of their genotype (type A or type B).

6. A Punnet square can be used to determine a persons genotype. Ex.

B. Paternity Testing –1. No blood group can appear in a child unless it is present in one of the parents.

2. Having the same blood type does not confirm paternity but it can exclude a person.

3. Most paternity blood tests look at many antigens that are associated with white blood cells. If a person can not be excluded using these tests there is a 90% probability he is the father.

DNA

1. DNA is a polymer. A polymer is a very large molecule made by linking together a series of repeating units. These units are known as nucleotides.

2. A nucleotide is composed of a sugar molecule, a phosphorus- containing group, and a nitrogen-containing molecule called a base.

3. There are only 4 types of bases associated with DNA: Adenine, Cytosine, Guanine, and Thymine.

4. Watson and Crick worked out the construction of the DNA molecule. It has the shape of a double helix. The long sides are made of the sugar and phosphate groups.

5. The bases connect the sides like the rungs of a ladder. 6. The bases only connect in specific ways. A with T and G with C. This is called base pairing.

7. Any base pair can follow another on the molecule. This allows for a huge number of possible sequences.

DNA at Work 8. DNA directs the production of complex molecules called proteins. Proteins are made by linking combinations of amino acids.

9. There are thousands of proteins made from only 20 amino acids. 10. The sequence of amino acids in a protein chain determines the shape and function of the protein.

Ex. Hemoglobin is a protein made of 4 amino acid chains. One of these chains has 7 amino acids linked together.

11. Sometimes the 6 th protein is changed from glutamate to valine. This small change causes a person to have sickle cell anemia.

12. The genetic information that determines the amino acids sequence for every protein is stored in DNA. For example the amino acids alanine is C-G-T, aspartate is C-T-A, always three!

Normal hemoglobin [G-C-T]-[G-A-T]-[G-A-G] proline glutamate glutamate Sickle cell [G-C-T]-[G-T-G]-[G-A-G] valine

13. By studying these base sequences scientists are isolating the genetic basis for diseases such as hemophilia, muscular dystrophy, and Huntington’s disease.

Human Genome Project The goal of the human genome project was to determine the order of bases on all 23 pairs of chromosomes. Why?

14. Because knowing where on a specific chromosome DNA codes for the production of a particular protein is useful for diagnosing and treating genetic diseases.

15. Mitochondrial DNA – mitochondria are cellular organelles responsible for energy production. There are several loops of DNA located in the mitochondria that are associated with energy generation.

16. Because each cell contains hundreds or thousands of mitochondria and each mitochondria contains several loops, there is much more DNA here than in the nucleus.

Drawbacks –Because this mtDNA comes only from the mother, all her children will have the same mtDNA. –It is much more expensive and time consuming to analyze.

17. The Combined DNA Index System (CODIS). In all 50 states DNA from convicted criminals is collected and placed in a database.

18. CODIS is the name of the software system that maintains local, state, and national databases of DNA profiles from convicted offenders, unsolved crime scene evidence, and missing person profiles.