Lab: Blood Samples

In your lab notebook, choose 4 different slides of blood samples and draw and label what you see at 400X.

Blood

Blood Evidence Blood typing = class evidence DNA profiling = individual evidence Blood-spatter: recreate crime scene

History of the study of blood 2500 B.C. Egyptians - bloodletting to cure diseases 500 B.C. Greeks – distinguished between arteries and veins 1659 A.D. Leeuwenhoek – view blood cells with microscope 1795 First blood transfusion performed 1901 Landsteiner – discovered 3 blood types (A, B, O)

1902 Decastello – discovered AB blood type 1922 Oliver – established blood donor service 1935 Mayo Clinic – developed a method to store blood for transfusions 1900s Kastle – developed first presumptive blood test 1959 Belgian Congo – first AIDS case recorded 1984 Gallo – identified virus causing AIDS 1987-2002 Development of blood-screening tests for infectious disease

Composition of Blood Cells (45%) Plasma (55%) red blood cells (RBC) white blood cells (WBC) Platelets Plasma (55%) 90% water Dissolved proteins (antibodies, hormones, clotting factors) Nutrients (O2, glucose, amino acids, salts, minerals) Wastes (urea, CO2)

Red Blood Cells Erythrocytes carry gases (oxygen, carbon dioxide) produced in bone marrow no internal organelles (no nucleus) hemoglobin is iron-containing protein that binds to O2 gives blood the red color

White Blood Cells Leukocytes fights disease and foreign invaders produced in bone marrow true cell – has nucleus

Platelets Tiny cell fragments Helps in blood clotting

Kastle-Meyer Presumptive Blood Test

If blood is present, swab will turn PINK. Procedures Wet cotton swab with distilled water and gently rub on stain Ethyl alcohol: breaks open cells, exposes hemoglobin Phenolphthalein (Kastle-Meyer Reagent): reducing agent; turns pink when oxidized Hydrogen peroxide: reacts with hemoglobin If blood is present, swab will turn PINK.

False Positives Some non-blood substances can yield a positive Kastle-Meyer test: vegetables with peroxidases (potatoes, beets, horseradish, broccoli, cauliflower) copper and nickel salts

Blood Typing

Why do blood typing? Less expensive and quicker than DNA profiling Class evidence Can be used to link or exclude suspect to crime scene (but doesn’t prove guilt)

Discovery of Blood Types Karl Landsteiner (1901) Blood from one person did not always mix freely with another person Clumping of mixed blood results in death Cell-Surface Proteins (RBC’s): A and B proteins Rh factor proteins Antibody reaction test used to identify blood types

ABO Blood Types 42% 12% 3% 43% Type A: has A antigen on surface of RBC Type B: has B antigen Type AB: has both A & B antigens Type O: has no antigens on surface

Antibodies Our bodies have the ability to recognize between own cells (self) and foreign invaders (non-self) White blood cells engulf and digest invaders Antibodies: Y-shaped proteins secreted by WBC’s which aid in immune response Antibodies bind to antigens (foreign substance or cell that reacts to antibodies)

Antibodies Type A: makes anti-B antibodies Type B: makes anti-A antibodies Type AB: no antibodies Type O: makes anti-A and anti-B antibodies

Antigen-Antibody Response Immune system attacks and destroys foreign invaders: WBC’s make antibodies that attach to foreign proteins WBC’s engulf invader Agglutination: clumping of blood cells

Rh Factor Rh protein found on RBC’s when Alexander Weiner worked with Rhesus monkeys (1940) Rh+ : 85% Rh- : 15%

Blood Typing Analysis

Blood Typing Analysis Blood sample mixed with 3 antibodies If blood clumps, proteins are present If no clumps, no proteins are present Anti-A antibody test Rh antibody test Anti-B antibody test

Other forms of identification Additional enzymes and proteins have been found in the blood: Phosphoglucomutase (PGM) Adenylate kinase (AK) Adenosine deaminase (ADA) Esterase D (EsD) Glucose-6-phosphate dehydrogenase (G-6-PD) Polymorphic proteins: Group-specific Components (Gc) and haptoglobins (Hp)