BLOODFacts, Factors and

Inheritance

BLOOD COMPOSITION 55% of the blood consists of plasma 45% consists of formed elements

44% of the formed elements consist of erythrocytes

1% consists of leukocytes and platelets which is also called the buffy coat

plasma

erythrocytes

buffy coat

PLASMA The liquid component of

blood 90% of the plasma is made

up of water 8% is made up of proteins 2% is made up of several

ions

BLOOD CELLS Erythrocytes: red

blood cells; function to transport oxygen

Leukocytes: white blood cells; function to protect the body

Platelets: cell fragments that function to clot the blood

BLOOD FACTORS Blood cells, like other cells in the body,

have proteins or factors located on their surfaces

These factors can be antigens, substances that can cause the immune system to respond

There are 3 important blood factors used to type a person’s blood:The ABO SystemThe MNS SystemThe Rh Factor

ABO SYSTEM In the ABO system there are two

different blood proteins: A and B The inheritance of these factors is based

on codominance of the A and B proteins In codominance, both alleles (different

forms of a gene) in the heterozygote express themselves fully

There are 3 different blood alleles:The A and B genes are both dominantThe o gene is recessive

ABO SYSTEM (CONT.) Based on the 3 genes there are 4

possible phenotypes:Type A bloodType B bloodType AB bloodType O blood

There are 6 possible genotypes:Possible Genotyp

esAA Ao BB Bo AB oo

Blood Types

Type A Type A Type B Type B Type AB Type O

ABO SYSTEM (CONT.) The inheritance of the ABO system can

be predicted using Punnett squares EX: A woman who is heterozygous for

Type A blood has a child with a man who is heterozygous for Type B blood. What are the possible genotypes and phenotypes of their child?A o

B

o

AB

ooAo

BoGenotypes: AB, Bo, Ao, oo

Phenotypes: Type AB, Type B, Type A, Type O

ABO SYSTEM (CONT.) This system is important not only in

forensics but in the medical field It is important for blood transfusions It is essential that the ABO blood types

match to prevent the blood from clumping

ABO SYSTEM (CONT.) Type A Blood:

Has A antigens and anti-B antibodies

If this person receives type B or type AB blood, the blood will clump as the anti-B antibodies attack the B antigens

Can receive type A and type O bloodMakes up 40% of the population

ABO SYSTEM (CONT.) Type B Blood:

Has B antigens and anti-A antibodies If this person receives type A or type AB

blood, the blood will clumpCan receive type B and type O bloodMakes up 11% of the population

ABO SYSTEM (CONT.) Type AB Blood:

Has A and B antigens and no ABO antibodies

Because this person doesn’t have ABO antibodies, they can receive any type blood, making this person the universal recipient

Makes up 4% of the population

ABO SYSTEM (CONT.) Type O Blood:

Has no antigens and anti-A and anti-B antibodies

Because this person doesn’t have antigens, they can donate to any type blood, making this person the universal donor

Can only receive type O bloodMakes up 45% of the population

MNS SYSTEM Similar to the ABO System A person carries either the M protein,

the N protein or the S protein on their blood cells

M is found in 30% of the population N is found in 22% of the population S is found in 48% of the population

Rh FACTOR The Rh protein can be found on the

surface of the blood cell Rh+: the person has the Rh antigen; it

is found in 84% of the population Rh-: the person does not have the Rh

antigen; makes up 16% of the population

O+ 38 percent of population O- 7 percent of populationA+ 34 percent of population A- 6 percent of populationB+ 9 percent of population B- 2 percent of populationAB+ 3 percent of population AB- 1 percent of population

CALCULATING PROBABILITIES Knowing the percentages of the

population with the different blood factors can be used to determine the likelihood of a certain combination of blood factors

By multiplying the ratios of the types, you can determine the probability of having a certain blood type

CALCULATING PROBABILITIES (CONT.) EX: What is the probability of a person

having blood type A and N and being Rh-?A N Rh-40% x 22% x 16% = ?.40 x .22 x .16 = .01

1 out of every 100 people would have blood type A and N and be Rh-