Blood and Blood Evidence
SEROLOGY
• Serology- the study of blood
– 1901- Karl Landsteiner discovers ABo blood
groups.
• 29 years later was awarded Nobel Prize for this feat.
– 1937- Rh factor was identified
– Up until early 1990’s many other blood factors
were being studied in an attempt to individualize
blood evidence
• class vs individual evidence
Composition of Blood
Composition of Blood
PLASMA (55%)- fluid portion of blood
* similar to salt water
-mainly water
-dissolved salts, nutrients, proteins,
antibodies, hormones ect…
SUSPENDED MATERIALS (45%)- “free
floating” materials/cells
*Red blood cells = ERYTHROCYTES
-carry oxygen
*White blood cells = LEUKOCYTES
-fight disease and foreign invaders
*platelets = THROMBOCYTES
-blood clotting and repair of
damaged blood vessels
KEY TERM
• Antigens- substances, usually proteins, that
can be found on the surface of our cells.
– Creates ABo blood group
– Creates Rh+/Rh- blood group
– Many other blood groups have been identified as
well
Blood Typing
ABo
3 alleles within our population
A = Allele coding for type A surface proteins
B = Allele coding for type B surface proteins
o = Allele coding for NO surface proteins
A & B alleles are codominant
o is recessive to both the A and B allele
Each person inherits 1 allele from each parent to
determine their ABo blood type
ABo Blood Groups
Phenotypes and Genotypes
Phenotypes
AA or Ao
BB or Bo
AB ONLY
GENOTYPES???
oo ONLY
Sample Problems
#1
If a woman who is heterozygous with type A blood
(Ao) marries a man with type O blood, what is the
probability that their children will have type A
blood? B blood? AB blood? O blood?
#2
A woman who is homozygous with type B blood
(BB) has a child out of wedlock that has type O
blood. She files a paternity suit against a man with
type O blood. Is the lawsuit valid?
Blood Typing
Rh Factor
• Rh factor is another type of surface protein which may be produced
on the surface of our cells.
• Rh+ (producing Rh protein) is dominant over being Rh- (not
producing Rh protein)
• R = allele for production of Rh protein (Rh+)
• r = allele for NO Rh protein (Rh-)
• Each person inherits 1 allele from each parent
GENOTYPES AND PHENOTYPES
RR = Rh+ blood
Rr = Rh+ blood
rr = Rh- blood
Sample Problems
#3
• A man who is Rh- marries a woman who is
heterozygous with Rh+ blood. What is the
probability that their children will be Rh+? Rh-?
#4
• A woman who is homozygous with Rh+ blood
marries a man who is heterozygous with Rh+
blood. Is it possible for them to have a child who
is Rh-?
Using Blood Typing as Class Evidence
• Identifies the presence or absence of
particular proteins embedded in the cell
• Quicker and less expensive than DNA
profiling
• Produces class evidence but can still link a
suspect to a crime scene or exclude a suspect
US Population and Blood Groups
• US Population & ABo Blood Grouping
Type A Blood – 42%
Type AB Blood – 3%
Type B Blood – 12%
Type O Blood – 43%
• US Population and Rh Blood Grouping
Rh+ = 85%
Rh- = 15%
• US Population and MN Blood Grouping (another
blood group not mentioned yet)
MM – 30%
MN – 48%
NN – 22%
Sample Problems
• Sample Problem #5
Calculate the probability of person being Type 0
Blood and Rh- (O- Blood Type).
• Sample Problem #6
Calculate the probability of a person having…
AB / Rh+ / MM .