1. Forensics Tests for the Presence of Blood
1. Kastle-Meyer color test – uses a chemical called phenolphthalein that turns dark pink in the presence of hemoglobin.
Certain vegetable materials (potatoes, horseradish) can cause a false positive result

2. Hemastix strips – turn green in the presence of blood

3. it’s sprayed on, so large areas can be screened
3. Luminol test – produces light in the presence of blood. Needs to be in a darkened place to see it.
it’s sprayed on, so large areas can be screened

4. 4. Precipitin test – determines if the blood is of human or animal origin
Uses antibodies to human and some animals blood

5. Blood Spatter Analysis
Blood Spatter Analysis is important in interpreting the events that led to the blood.
Studies have concluded that:
The harder and less porous the surface, the less spatter
The pointed end of a bloodstain always faces its direction of travel
A drop of blood that strikes a surface at a right angle yields a circular stain. Other angles give a elongated shape.
Drawing lines through the long axis of several individual blood drops can find the origin of the blood spatter. The intersection of the lines is the point from which the blood came.

6. The Genetics of Blood Type
Humans have 46 chromosomes, each of which contains hundreds or thousands of genes.
Each gene codes for a specific protein.
Know the definitions of the following words:
Allele
Homozygous
Heterozygous
Phenotype
genotype

7. In human blood types, the A allele produces the A antigen, the B allele produces the B antigen, and the O allele doesn’t produces either antigen.
A and B are dominant to O
A and B are codominant with each other
Blood type A (phenotype) can be genotype AA or AO
Blood type B can be genotype BB or BO
Blood type AB must be genotype AB
Blood type O must be genotype OO

8. A Punnet square can be used to figure out the possible blood types of offspring
Practice:
What blood types are possible for the children of a type O parent and a type AB parent?
Can a father with blood type A and a mother with blood type B produce a child with blood type O? Justify your answer with a Punnet square
If a mother with blood type O and a father with blood type B produce a child with blood type O, what must the father’s genotype be?