Our blood comes in a few different varieties. Our red blood cells contain a protein called hemoglobin that binds to oxygen, allowing the cells to transport it throughout the body. But they also have another kind of complex protein on the outside of the cell membrane. These proteins known as antigens, communicate with white blood cells, immune cells, that protect against infection. Antigens serve as identifying markers, allowing the immune system to recognize your bodies own cells without attacking them as foreign bodies.
The two main kinds of antigens, A and B determine your blood type. The antigens are coded for three different alleles varieties of a particular gene. While the A and B alleles code for A and B antigens, the O allele codes for neither and because we inherit one copy of each gene from each parent. Every individual has two alleles determining blood type.
When these happen to be different, one over rides the other depending on their relative dominants, For blood types, the A and B alleles are both dominant while O is recessive. So A and A gives A blood, while B and B gives you type B.
If you inherit one of each, the resulting co dominance will produce both A and B antigens which is type AB. The O allele is recessive so either of the other will over ride it when they are paired resulting in either type A or type B. But if you happen to inherit two O’s instructions will be expressed that make blood cells without the A or the B antigen.
Also Read – Normal composition of blood