Multiple allelism refers to the presence of more than 2 contrasting alleles for a gene.

1. MULTIPLE ALLELES………
Dr.V.Jeyanthi kumari,
Assistant Professor of Zoology,
A.P.C.Mahalaxmi College for Women,
Thoothukudi

2. Definition
A set of 3 or more alleles of the same gene on the homologous
chromosomes to control a particular trait is called multiple alleles.
ABO Blood Group
Landsteiner found 4 types of human beings depending on the
presence or absence of antigens in the blood. They are A, B, AB, and
O.
1. A group person contains antigen A on the RBC and antibody b
2. B group persons contain antigen B on the RBC and antibody a
3. AB group persons contain both ags A and B on the RBC
4. O group person contain no antigens on the RBC but both a&b abs.

3. GROUP Antigen Antibody
A A b
B B a
AB AB -
O - ab

4. 1. The synthesis of antigen A is controlled by dominant alleleLA.
2. Antigen B synthesis is controlled by another dominant allele LB.
3 The absence of antigens due to the presence of recessive allele LO
Thus 3 alleles are responsible for ABO blood group.
P Father × Mother
Group A Group B
LA LA LB LO
G LA LB LO
F1 LA LB LA LO
AB A

5. P : Father * Mother
Group A Group B
LA LO LB LO
G : LA LO LB LO
F1 : LA LB LA LO LB LO LO LO
AB A B O

6. P Group A * Group B
LA LA LB LB
G LA LB
F1 LA LB
LA LB * LA LB
G LA LB LA LB
F2 LA LA LA LB LALB LB LB
A AB AB B
The inheritance of ABO blood groups follows Simple Mendelian
inheritance.

7. APPLICATION OF ABO BLOOD GROUP
1.BLOOD TRANSFUSION
1. The transfer of blood from one person to another is called blood
transfusion.
2. Blood transfusion is a life saving prices in accidents and operation
cases.
3. Successful blood transfusion needs a thorough blood group testing.
4. The person donating blood is called donor.
5. The person receiving blood is called recipient.
6. O group personis the universal donor. AB group person is called
universal recipient.
DISPUTED PARENTAGE
The parents of a disputed baby can be confirmed by testing the blood
groups of the doubtful persons
Similarly, the claim of 2mothers for a single child can be settled by
blood group testing.

8. 3.IDENTIFICATION OF CULPRITS
In murder cases, the culprits can be confirmed, if the culprits blood stain
is available at the place of murder.