What is the inheritance pattern for the blood type genes- a, b,o?

It's carried out by a sugar "i", it can be dominant (Homozygous, Heterozygous) & recessive. A & B are co-dominant to each other whereas O is recessive to both of them.

Hope this helps!

Individuals with type O blood do not produce ABO antigens.  Therefore, their blood normally will not be rejected when it is given to others with different ABO types.  As a result, type O people are universal donors for transfusions, but they can receive only type O blood themselves.  Those who have type AB blood do not make any ABO antibodies.  Their blood does not discriminate against any other ABO type.  Consequently, they are universal receivers for transfusions, but their blood will be agglutinated when given to people with every other type because they produce both kinds of antigens.