Blood Types Codominance When two or more alleles

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 (markers on your cells) 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 blood genotypes = IAIA or IAi Has only A antigens on the surface Has Anti-B antibodies A A A

Type B blood genotypes = IBi or IBIB Has only B antigens on the surface Has Anti-A antibodies B B B

Type AB blood genotype = IAIB Has A and B antigens on the surface B A A No antibodies! B B A A B

Type O blood genotype = IO IO or ii Has NO antigens on the surface Makes Anti-A and Anti-B antibodies

Fig. 14. 21

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

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

What happens if the wrong blood type is given?