jimtrue.com : school : CJT2260 : 2003-09-11: Confirmatory Tests & Conventional Serology
Posted by Jim True on September 11, 2003 6:25 AM. Last Updated October 22, 2006 9:23 PM
Disclaimer for all material noted here is at the bottom of this web page.
"ABO Typing Online Quiz":http://anthro.palomar.edu/blood/quizzes/bldquiz1.htm -- Nice little quiz on the ABO system and RH Serology system. Helpful guide.
Main difference between clinical and forensic serologists: clinical works with fresh blood, forensic works with dried blood stains.
Most biological samples fall under the category of "class" type evidence, and can be used to positively *exonerate or exclude* individuals.
Blood: Takayama, Teichmann, Ouchterlony. Concentrate on Takyama and Ouchterlony.
Takayama -- Microcrystalline test; will form crystals after several reagents (figure 11.7) Rhomboid, Crystalline structures. Developed in 1912.
Ouchterlony -- Species determination test (not to determine if it's blood, but to determine if it's human or not).
ABO Typing -- Developed by Karl Landsteiner in 1900. A long time ago people were playing around with the concept of transfusing blood from other people (or from a Lion to a King) and realized that cross-species blood transfusions couldn't work. Didn't account for incompatibilities.
Pope banned all blood transfusions; in 1850's, John Blondell started transfusions again; was only going to transfuse blood from close relatives, or husband to wife. Still only had 50% success ratio with the blood transfusions. The 50% success ratio was based on O typing and that blood typing would also follow down genetic traits in families.
45% - O, Universal donor. More dominate would be the O blood type. Incas were doing blood transfusions way, way back. Later, their transfusions became about 100% effective because most people in South America had O type blood.
Noticed Antigens in the red blood cells. Could type blood based on the Antigens present.
| *Antigens:* |
| A | A Type |
| B | B Type |
| AB | AB |
| O | H |
| Rh | D |
| *P.193, Population frequencies* |
| A | 40% |
| B | 10% |
| AB | 5% |
| O | 45% |
| Rh | +85% |
RH: Those who have the D Antigen are Postive; 15% are negative and don't have the antigen.
*Why we have blood?*
Billions of years ago there were simple little organisms floating around in the sea. All they had to do was pass nutrients directly through their cell membranes into and out of their bodies. As they evolved, it was no longer efficient to transfuse nutrients through their cells. Created little cavities for holding sea water; sea water has several things in common with sea water (same pH).
Used to transport oxygen, carbon dioxide, hormones, etc.
55% Liquid medium, called Plasma, 45% called formed elements. Red blood cells (erythrocytes), White Blood Cells, Thrombocytes
RBC's 99%, Anucleate (no nucleus) - do not reproduce themselves; formed in the bone marrow. Can better use their space for hemoglobin for carrying oxygen and carbon dioxide. Antigens are part and parcel of the cell membrane (kind of like chocolate chips on a chocolate chip cookie).
WBC's - 0.2%, fight off infection (part of the bodies defense system against disease). All have a Nucleus. When looking for DNA in blood, you're looking for the white blood cells.
Thrombocytes - 0.6 - 1.0% (also called platelets) are necessary for clotting. Combine with fibrin to create a clot.
Plasma - Antibodies are found in the plasma (antibodies cause agglutination if two incompatible blood types are mixed). Antibodies are bivalent, meaning they have two reactive sites on them.
|*Type*|*Percentage*|*Antigen*|*Antibody(ies)*|
|O|45%| H |both A&B|
|A|40%| A| AntiB|
|B|10% | B| AntiA|
|AB|5%| none | neither |
O Universal Donor, but can only receive from O type
AB Universal Recipient, but can only donate to another AB
*Secretor Status* -- 80%
Genetics is what will determine if a person is a secretor or not. What secretor means is that a persons blood type antigens will show up in other body fluids, most likely *seminal fluid & saliva*.
Absorption-Elution method is an indirect method of typing dried stains; can be used on stains up to 11 years old. pg 195.
*Enzymes*
Proteins that are involved in the regulation of chemical reactions. p.197 (table of forensically important enzymes). p.199, frequency and population of those enzymes.
Enzymes come in a variety of different shapes and subtypes. *Polymorphic*, meaning "poly" (many) and "morphic" (shapes).
Polymorphic enzymes can be further broken down into *Isoenzymes*. PGM can be broken down into multiple subtypes or Isoenzymes of this Polymorphic enzyme. Can be used to further break down the classification of the evidence, especially when there is no DNA present.
*Example:* Out of 1000 population
Suspect has Type B blood. 10%, 100 possible suspects
Add Rh Positive factor: Multiply 10% x 85% for new percentage of the 1000 population that could be possible suspects.
Add PGM -1 (1.8%), Multiply 10% x 85% x 1.8% for final population percentage.
Leftover plasma, yellowish jelly-like substance remaining after clotting is called Serum.
*Conventional Serological Testing* includes the following types of tests:
* Confirmatory Tests - Takayama
* Species Determination - Ouchterlony
* ABO/Enzyme Grouping -
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