Blood Basics - Forensic Science - Lecture Slides, Slides of Forensics

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Blood Basics

What makes up our blood?

 RED BLOOD CELLS (Erythrocytes) – The most abundant cells in our blood; they are produced in the bone marrow and contain a protein called hemoglobin that carries oxygen to our cells.  WHITE BLOOD CELLS (Leukocytes ) – They are part of the immune system and destroy infectious agents called pathogens.  PLASMA – This is the yellowish liquid portion of blood that contains electrolytes, nutrients and vitamins, hormones, clotting factors, and proteins such as antibodies to fight infection.  PLATELETS (Thrombocytes ) – The clotting factors that are carried in the plasma; they clot together in a process called coagulation to seal a wound and prevent a loss of blood.

Karl Landsteiner

 In 1901 discovered blood types

 Earned him a Nobel Prize

 Prior to this discover, transfusions typically resulted in coagulation resulting in immediate death.

 Over 100 antigens have been located in the blood, the two most important are ABO and Rh

Genetics of Blood Types

 Your blood type is established before you are BORN , by specific GENES inherited from your parents.

 These two genes - one gene from your MOTHER and one from your FATHER - determine your blood type by causing proteins called AGGLUTINOGENS (a type of antigen) to exist on the surface of all of your red blood cells.

Blood Types

 A person’s blood type has two components:

 ABO group  Rhesus (Rh) factor

Rhesus Group

 The Rh factor or Rhesus group was named for the Rhesus monkey (the location where it was first identified).

 There are two possible phenotypes:

 Rh+ (a person displays Rh antigen on their RBCs)  Rh- (a person displays no antigen on their RBC’s)

Transfusion Concerns

 Can a person with positive blood, receive a transplant from someone with negative blood?  Absolutely!! Because the negative blood has no surface antigen, the body doesn’t even realize it’s there.  Can a person with negative blood, receive a transplant from someone with positive blood?  No!! The antigen-antibody reaction would be life threatening

Rhesus Inheritance

 The Rhesus factor follows the rules of simple Mendelian inheritance.

 There are two alleles (+ and -) with + being the dominant allele.

ABO Groups

 There are four possible phenotypes

 A  B  AB  O

 A person’s phenotype tells us the surface antigen (agglutinogen) that their RBCs display

Distribution

Distribution

ABO Inheritance

 There are 3 possible alleles (A, B, O).

 A and B are codominant over O.