traits controlled by multiple alleles means that there is more than 2 alleles that control a trait....

Traits Controlled byMultiple Alleles

Means that there is more than 2 alleles that control a trait. (3 or more alleles)

Blood types are an example of multiple alleles in humans

Blood Types

• There are 4 types of blood:– Type A– Type B– Type AB– Type O

What does it mean to have a certain type of blood?

• When we talk about types of blood, people can have any of the four types.

• When we stay that a person has a certain type of blood, we are saying that their red blood cells have a specific marker or I.D. on them that the body can recognize.

• This marker or I.D. is called an antigen.

• RBC are important because they carry oxygen to all areas of our body.

Type A blood

• For example, if a person was to have type A blood, their red blood cells would have A antigens covering their RBC.

RBCA

A

A

AA

AA

A

Type B Blood

• For example, if a person was to have type B blood, their red blood cells would have B antigens covering their RBC.

RBC B

BB B

B

B

BB

Type AB• For example, if a person was to have type AB

blood, their red blood cells would have A and B antigens covering their RBC.

• There is no such thing as an AB antigen. There is only A and B.

RBC

B

B

BB

A

A A

A

Type O

• Type O blood is special. People have no antigens on their RBC when they have type O blood.

• You can think of the O as a zero, for zero antigens.

RBC

Antibodies• An antibody is a protein in the body that “reads”

antigens and determines if they are foreign, do not belong, or native, belong in the body. If it recognizes the antigen as native, it leaves it alone. If it recognizes it as foreign, it will destroy the ENTIRE cell.

• In our bodies, we can make 2 types of antibodies that will attack and destroy RBCs.– A antibodies – attack and destroy RBCs with A antigens– B antibodies – attack and destroy RBCs with B antigens

Blood Types and the Antibodies They Produce

• If you have type A blood, your RBCs have A antigens. You will only make B antibodies. The reason for this is that B antibodies do not attack and destroy cells with A antigens, so your body will not destroy its RBCs.

• If you have type B blood, your RBCs have B antigens. You will only make A antibodies. The reason for this is that A antibodies do not attack and destroy cells with B antigens, so your body will not destroy its RBCs.

• If you have type AB blood, your RBCs have A and B antigens. You will make no antibodies. The reason for this is that you have both antigens. If you made either A or B antibodies, they would attack and destroy your RBCs.

• If you have type O blood, your RBCs have no antigens. Therefore, your body considers ANY antigen to be foreign, and it makes both A and B antibodies.

Why is it important to know what antibodies you make?

• It is important to know your blood type and therefore the antibodies you make incase you need a blood transfusion.

• If you are given the wrong type of blood, your antibodies will attack an destroy the new RBCs that you are being given. This will form clumps in your blood. If you are given enough of the wrong blood, you could die.

Type of Blood Antigens on RBC

Antibodies Produced in

Blood

Blood Types that can be

received from

Blood Types that can be donated to



Blood


received from


A



Blood


received from


A

B



Blood


received from


A

B

AB



Blood


received from


A

B

AB

O



Blood


received from


A A

B

AB

O



Blood


received from


A A

B B

AB

O



Blood


received from


A A

B B

AB A and B

O



Blood


received from


A A

B B

AB A and B

O None



Blood


received from


A A B

B B

AB A and B

O None



Blood


received from


A A B

B B A

AB A and B

O None



Blood


received from


A A B

B B A

AB A and B None

O None



Blood


received from


A A B

B B A

AB A and B None

O None A and B



Blood


received from


A A B A and O

B B A

AB A and B None

O None A and B



Blood


received from


A A B A and O

B B A B and O

AB A and B None

O None A and B



Blood


received from


A A B A and O

B B A B and O

AB A and B None A, B, AB, and O

O None A and B



Blood


received from


A A B A and O

B B A B and O


O None A and B O



Blood


received from


A A B A and O A and AB

B B A B and O


O None A and B O



Blood


received from



B B A B and O B and AB


O None A and B O



Blood


received from




AB A and B None A, B, AB, and O AB

O None A and B O



Blood


received from




AB A and B None A, B, AB, and O AB

O None A and B O A, B, AB, and O

Blood Typing

• If someone is in an accident and needs blood, the hospital would quickly run a blood typing test on that individual.

• They do this by mixing the patient’s blood with different antibodies. If they were to mix the patient’s blood with A antibodies, and it was to clot, it would tell the hospital that the patient has type A antigens and therefore, type A blood.

• If there is no time to waste, a patient would be given O- (O negative) blood, because there are no antigens to interact with any antibodies the patient might have.

Blood Type Alleles

• In blood types, both A and B are dominant over O.

• But A and B are not dominant over each other. They are both expressed simultaneously. They are co-dominant.

• Alleles– A = IA

– B = IB

– O= io

Possible Genotypes

• Blood Type A– IA IA or IA io

• Blood Type B– IB IB or IB io

• Blood Type AB– IA IB

• Blood Type O– io io

• The only way to be type AB blood is to have an allele for type A and an allele for type B.

• The only way to be type O blood is to have two alleles for type O.

Rh Factor• The Rh factor is what determines if you have positive or negative

blood. • If you have the Rh factor, you have positive blood, because you are

Rh positive. (A+, B+, AB+, and O+)

• If you do not have the Rh factor, you have negative blood, because you are Rh negative. (A-, B-, AB-, and O-)

• Rh is another type of antigen. • If you are Rh positive, you DO NOT make Rh antibodies.• If you are Rh negative, you DO make Rh antibodies. This is due to the

fact that, the Rh antigen is foreign, and your body will want to destroy it.

• Therefore, people with negative blood, can ONLY receive blood from other people with negative blood, as long as the blood type matches; however, people with positive blood can receive from people with either positive or negative blood, as long as the blood type matches.

traits controlled by multiple alleles means that there is more than 2 alleles that control a trait....

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