BLOOD GROUP INHERITANCE

In the human beings, the character blood group contains '4' Phenotypes. These are A, B, AB and O. These are first discovered by Landsteiner.

BLOOD GROUP INHERITANCE

The hereditary blood group antigens are 'A' and 'B'. These lie on R.B.C. The hereditary plasma antibodies are 'a' and 'b'. Both antigens and antibodies are proteins. The specific antigen reacts with specific antibody to form into agglutination or precipitation. For example 'A' antigen reacts with 'a' antibody to form into precipitate. Like wise 'B' antigen reacts with 'b' antibody to form into precipitate. The blood precipitation tests are useful to identify the blood groups and also for proper blood transfusion.

 

Name of the blood group, type of antigen, type of antibody present, donate to and receives from are represented in the following table.

'AB' group persons are said to be universal recipients due to the absence of antibodies. 'O' group persons are said to be universal donors due to the absence of both types of antigens.

BLOOD GROUPS-HEREDITARY

Normally one character contains two different alleles. The blood group antigen controlling genes lie on'9'th autosome. But the character blood group contains three types of alleles. They are 1A, 1B and 1°. Among the three types of alleles, "l°' is recessive to both 1A and 1s. Where as 1Aand 1B are co dominant.

BLOOD GROUP HERIDITARY

As the blood group character contains '3' different types of alleles, such alleles are called multiple alleles. Skin colour and height in human beings are also examples of multiple alleles.

The '4' Phenotypes of blood group contains '6' genotypes. The phenotypes and genotypes of blood group are represented in the following table.

2. BLOOD GROUPS OF PARENTS - EXPECTED GROUPS IN CHILDREN

A. If both the parents are heterozygous 'A' group, the possible blood groups in children would be 'A' and 'O'.

BLOOD GROUPS

B. If the parents are heterozygous 'A' and 'B', the possible blood groups in the children would be 'A', 'B', 'AB' and 'O'.

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3. USE OF KNOWING OF BLOOD GROUPS

i. for proper blood transfusion

ii. to decide that the father may not be a real father.

1. 'Rh' Blood groups:

The subsidiary blood group 'Rh' was first discovered in Rhesus monkey by Weisner and Steiner. The character 'Rh' contains two Phenotypes. These are Rh+ and Rh-. If the person contains 'Rh antigen on R.B.C., such person's blood group is called Rlr. If the 'Rh' antigen is absent on R.B.C, such person's blood group is called Rh-. 85% of the persons are Rlr.

2. 'Rh'alleles:

The two alleles of character 'Rh' Blood group are Rlr and Rh-. But hereditory Rh antibodies are absent.

3. Erythroblastosis foetalis:

When Rh" Lady marries a homozygous Rlr man, the first child escapes from death. But every embryo dies from second embryo onwards due to erythro blastosis foetalis. In this the 'Rh' antigens developed in the first embryo migrates to the blood of mother through the placenta. As the 'Rh' antigens are foreign to mother, the 'Rh' anti bodies are developed in the mother. As these are developed after the first delivery, the first embryo escapes from death. But from second embryo, every embryo dies as all ready synthesized 'Rh' antibodies migrate to the embryo through the placenta.

4. 'Rh' factor inheritance:

When 'Rh-' lady marries a heterozygous 'Rh+' man, the probable groups in children are heterozygous Rh+ and Rh-.

5. USE OF KNOWING OF Rh BLOOD GROUP

Rh BLOOD GROUP

i. for proper blood transfusion. 0-group is universal donor due to the absence of all types of antigens.

ii. to decide that the father may not be a real father.

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