chapter 8 blood “out damned spot! out, i say here’s the smell of the blood still, all the...

Chapter 8

Blood

“Out damned spot! Out, I say Here’s the smell of the blood still,All the perfumed of Arabia will not

Sweeten this little hand. Oh, Oh, Oh!”

—William Shakespeare’s Lady Macbeth, in Macbeth

Blood That an antibody and

an antigen of different types will agglutinate, or clump, when mixed together.

That the significance of the evidence depends on a characteristic’s relative occurrence in the population.

You will learn:

Blood You will be able to:

Determine whether a stain is blood.

Determine whether a bloodstain is human or animal blood.

Determine the blood type of a simulated bloodstain using the ABO/Rh system.

SerologyThe examination and analysis of body fluids

From 1950’s to 1980’s -- high importance

With DNA -- now a matter of economics

Blood Characteristics Plasma is the fluid portion of the

blood (55%) Cells (45%)

Erythrocytes are red blood cells. They are responsible for oxygen distribution.

Leukocytes are the white blood cells; they are responsible for “cleaning” the system of foreign invaders.

Platelets (proteins) are responsible for blood clotting

Serum is the liquid that separates from the blood when a clot is formed.

Parts of Blood

Unknown Stain at a SceneQuestions to be answered: Is it blood? Is it human blood? Whose is it?

Determine blood type, alcohol content, drugs present

Determine the method(s) in which blood may have been deposited

Presumptive Tests forBlood Determination

Kastle-Meyer color test—a mixture of phenolphthalein and hydrogen peroxide; the hemoglobin will cause the formation of a deep pink color if blood is present

Hematest® tablet—reacts with the heme group in blood causing a blue-green color

Luminol test—reaction with blood to produce light

Testing for Blood

Both the Kastle Meyer and Luminol test for presence of blood are examples of chemical reactions.

Human vs Animal Blood

Microscopic observation

Precipitin test—blood is injected into a rabbit; antibodies are formed; the rabbit’s blood is extracted as an antiserum; the antiserum is placed on sample blood. The sample will react with human proteins, if human blood is present. This test is very sensitive and requires only a small amount of blood.

Animal Blood

Larger nucleic red blood cells

Frog Blood

Human Blood Red blood cells are most

numerous; 5 to 6 million per mm3

White blood cells are larger and less numerous; 5 to 10,000 per mm3

Platelets are tiny, cellular fragments; 350 to 500,00 per mm3

Secretors

80% of the population are secretors. Their blood-type antigens are found in high concentration in their body fluids such as saliva, semen, vaginal secretions and gastric juice.

Historical Perspective

of Blood TypingKarl Landsteiner

1900

4 types

In 1940 Rh factor

85% of Caucasions

94% Black Americans

99% Asians

How is our blood type determined?

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

You receive one gene from your MOTHER and one from your FATHER.

These two genes determine your blood type by causing proteins called AGGLUTINOGENS to exist on the surface of all of your red blood cells.

Blood Typing A-B-O and Rh systems are the most important in identifying blood

An individual that is type A has A antigens on his/her red blood cells

Type B has B antigens Type AB has both A and B antigens Type O has neither A nor B antigens

Agglutination For every antigen there is a specific antibody that will react with it to form clumps (agglutination)

For example, Red blood cells containing B antigens will react in the presence of B antibodies

What are blood types?

http://learn.genetics.utah.edu/units/basics/blood/types.cfm

There are 3 alleles or genes for blood type: A, B, & O. Since we have 2 genes, there are 6 possible combinations.

Blood Types

AA or AO = Type ABB or BO = Type B

OO = Type OAB = Type AB

http://www.lanecountyblood.org/images/other/bloodfacts.jpg

45%

40%

11%

4%

How common are the 4 blood types?

Blood Groups

Type Antigen Antibody Can GiveBlood To

Can GetBlood From

A

B

AB

O

A

B

A and B

NeitherA nor B

B

A

NeitherA nor B

A and B

A, AB O, A

B, AB O , B

AB

A, B, O, AB

A, B, O, AB

O

Rh Factors Scientists sometimes study Rhesus monkeys to learn

more about the human anatomy because there are certain similarities between the two species. While studying Rhesus monkeys, a certain blood protein was discovered. This protein is also present in the blood of some people. Other people, however, do not have the protein.

The presence of the protein, or lack of it, is referred to as the Rh (for Rhesus) factor.

If your blood does contain the protein, your blood is said to be Rh positive (Rh+). If your blood does not contain the protein, your blood is said to be Rh negative (Rh-).

A+ A-B+ B-

AB+ AB-O+ O-

http://www.fi.edu/biosci/blood/rh.html

Rh factor Determined by presence of another antigen

People having antigen are Rh +

People not having are Rh-

Blood Typing Use the results shown to determine the blood type

for each sample.

- = No Clumps

+ = Clump

A

B

Rh

Blood Type: ___

To determine a person’s blood type, we add three different serums to blood samples and see if clumps form.

Clumps = Positive (+)No Clumps = Negative (-)

What would the blood type be for this sample?

A

B

Rh

Blood Type: ___

A

B

Rh

Blood Type: ___

A

B

Rh

Blood Type: ___

A

B

Rh

Blood Type: ___

A

B

Rh

Blood Type: ___

Blood Typing Use the results shown to determine the blood type for each sample.

- = absent

+ = present