Blood Types

Co-dominance

• When two or more alleles for a gene contribute to the phenotype

Blood type alleles

• IA = type A marker (antigen)

• IB = type B marker (antigen)

• IO or just I = No markers (antigen)

• Antigen – means marker on the surface of a cell

**antigens are how your body can identify which cells belong to you and which are foreign**

Antigens vs. Antibodies

• Antigens are how your body recognizes which cells are yours and which cells are foreign.

• Antibodies are what your body produces to fight off any cell that is not “marked” as yours.

THINK – PAIR - SHARE

• If there are 3 co-dominant alleles, how many different blood types (phenotypes) are possible?

• 4 possible blood types– A– B– AB– O

Type A bloodgenotypes = IAIA or IAIO

AAA

A

A

Has only A antigens on the surface

Has Anti-B antibodies

Type B bloodgenotypes = IBIO or IBIB

Has only B antigens on the surface

Has Anti-A antibodiesB

B

B

B

B

Type AB bloodgenotype = IAIB

A

A

A

AB

B

B

B

Has A and B antigens on the surface

No antibodies!

Type O bloodgenotype = IO IO

Has NO antigens on the surface

Makes Anti-A and Anti-B antibodies

Rh Blood Group

• Rh positive indicates presence of antigen D

• Rh negative indicates absence of Antigen D

• Rh antigens, like A and B antigens are inherited and present from birth

• Anti-D antibodies are not produced until after an individual is sensitized to antigen D

Fig. 14.21

What blood can I receive?Blood type: Can receive from: Can give to:

Type A A or O A or AB

Type B B or O B or AB

Type AB A, B, AB or O*UNIVERSAL RECIPIENT

AB only

Type O O only A, B and AB*UNIVERSAL DONOR

What happens if the wrong blood

type is given?