Introduction: A person’s blood type is an inherited trait governing special marker proteins appear- ing on the surface of their red blood cells. Blood typing is important, because it governs who an individual can give or receive blood donations from; blood with proteins markers not present in their own blood will be rejected by an individual’s immune system. There are two separate genes that govern blood type; the ABO gene has two dominant options, A and B, and a recessive option called O. For example, an individual with AO or AA would present the A protein, and an individual with AB will present both the A and B proteins on their blood; an individual with OO has no proteins from this gene. The Rh gene has two options; the dominant option is called positive (or + for short), while the recessive option is called negative or null (or – for short). For example, an individual with ++ or +– would present the Rh protein on their blood, while an individual with – – would not present the Rh protein. Together, these genes give your blood type, which can be one of O+, O-, A+, A-, B+, B-, AB+, or AB-. The percentage of individuals in the United States with each of the blood types are as follows (listed in increasing order of likelihood): • AB-: 0.6% • B-: 1.5% • AB+: 3.4% • A-: 6.3% • O-: 6.6% • B+: 8.5% • A+: 35.7% • O+: 37.4% Question 1: What is the conditional probability that someone has the B marker given that they have the Rh marker?

Introduction: A person’s blood type is an inherited trait governing special marker proteins appear-
ing on the surface of their red blood cells. Blood typing is important, because it governs who an
individual can give or receive blood donations from; blood with proteins markers not present in their
own blood will be rejected by an individual’s immune system.
There are two separate genes that govern blood type; the ABO gene has two dominant options, A
and B, and a recessive option called O. For example, an individual with AO or AA would present
the A protein, and an individual with AB will present both the A and B proteins on their blood;
an individual with OO has no proteins from this gene. The Rh gene has two options; the dominant
option is called positive (or + for short), while the recessive option is called negative or null (or –
for short). For example, an individual with ++ or +– would present the Rh protein on their blood,
while an individual with – – would not present the Rh protein.
Together, these genes give your blood type, which can be one of O+, O-, A+, A-, B+, B-, AB+, or
AB-.

The percentage of individuals in the United States with each of the blood types are as
follows (listed in increasing order of likelihood):
• AB-: 0.6%
• B-: 1.5%
• AB+: 3.4%
• A-: 6.3%

• O-: 6.6%
• B+: 8.5%
• A+: 35.7%
• O+: 37.4%

Question 1: What is the conditional probability that someone has the B marker given that they
have the Rh marker?