Most of us know our blood type. Have you ever wonder how did you get that blood type? What made your blood to be called as type A or B or O?
When you have a cut or a wound, a red colour fluid (Blood) runs out of it. It’s quite common to every one of us. Everything looks same in color and smell for sure. Yet, it is differentiated into different types.
What actually makes the difference is the ‘Antigens’ in it. Yes, blood is classified into different types according to the presence and absence of molecules called antigens. Antigens are present on the surface of every red blood cell in a human’s body. Antigens are either the proteins or complexes of sugar molecules which are called as polysaccharides.
Blood group antigen proteins serve a variety of functions within the cell membrane of red blood cells. These protein functions include transporting other proteins and molecules into and out of the cell, helps in maintaining cell structure, attaching to other cells and molecules and participating in chemical reactions. Apart from all these, the basic and major function of blood group antigen is to recognise foreign cells in the bloodstream.
Whenever a blood group antigen recognizes foreign cells, it gives an immune response. It produces antibodies against foreign cells which attacks and destroys them.
So, Based on the presence and absence of polysaccharides on the surface of red blood cells, blood groups are classified into A, B, AB or O.
‘A’ and ‘B’ are the two different polysaccharides formed from a precursor substance that is modified by the enzyme product of either the ‘IA’ allele or the ‘IB’ allele. You get these ‘IA’ and ‘IB ‘allele from each your parent during the formation of zygote.
- People having genotype ‘IAIA’ produce red blood cells having only ‘A’ polysaccharide and are said to have blood type A.
- Similarly, those having genotype ‘IBIB’ produce red blood cells having only ‘B’ polysaccharide and are said to have blood type ‘B’.
- Heterozygous ‘IAIB’ people have red blood cells having both ‘A’ and ‘B’ polysaccharide and have blood type ‘AB’.
- Homozygous ‘IoIo’ lack both the polysaccharide A and B, they are said to have blood type ‘O’.
Understanding Blood Group Genotype
1. ‘IAIB’ genotype illustrate codominance, because it has got the characteristics of both homozygous genotypes (both ‘IA’ and ‘IB’).
2. The allele ‘IO’ does not show codominance. It encodes a defective enzyme that doesn’t change the precursor. Neither the A nor the B type of polysaccharide is present.
With respect to the above explanation it is quite clear that, in ‘IAIO’ heterozygotes, polysaccharide A is present and are said to have blood type A. In ‘IBIO’ heterozygotes, polysaccharide B is present and has got blood type B.
If Father has Blood Group A and Mother has Blood Group B , What will be the blood group of children?
After understanding the details about blood group and how it’s classified. We should be able to derive the blood group of children provided we know the blood group of father and mother.
- Father has Blood group A; So he is having IA IO Alleles. Here, A is codominance and O is recessive allele.
- Mother has blood group B; So she has IB IO alleles. Here, A is codominance and O is recessive allele.
- If Child receives IA from father and IO from Mother; then S/he will have ‘IAIO’ alleles so He will be having Blood group of type ‘A’
- If Child receives IA from father and IB from Mother; then S/he will have ‘IAIB’ alleles so S/he will be having Blood group of type ‘AB’
- If Child receives ‘IO’ from father and ‘IB’ from Mother; then S/he will have ‘IOIB’ alleles so S/he will be having Blood group of type ‘B’
- If Child receives IO from father and IO from Mother; then S/he will have ‘IOIO’ alleles so S/he will be having Blood group of type ‘O’
Apart from that, there is one more protein that plays its crucial role in grouping of blood. That is Rh factor (Rhesus D). Based on the presence or absence of this RhD (Rhesus D) ABO blood type is followed by plus or minus. If Rh factor is present it is called positive, indicated as A+ve, B+ve, AB+ve, O+ve. If Rh factor is absent it is called negative, indicated as A-ve, B-ve, AB-ve, O-ve.
I hope this clear’s out and helps you understand much more about blood group types. If you liked this, rate this post and let us know your comments, suggestions!