1. +
MULTIPLE ALLELE
PRESENTED BY:
MARIE ELAINE S SEBASTIAN

2. +
MULTIPLE ALLELE
Anallele which consists of three (3) or
more alleles of the same gene
However, individuals within the
population are only able to hold two of
them
It can only be studied in populations

3. +
The ABO
Blood Group
A simple case of multiple alleles in which
there are 3 alternative alleles of one gene

4. +
ABO Blood Group
Discovered by Karl Landsteiner in early 1900s
 An excellent example of multiple allele inheritance is human
blood type. Blood type exists as four possible phenotypes: A,
B, AB, & O.
 There are 3 alleles (A, B and O) for the gene that determines
blood type.
 One combination of alleles in the ABO system exhibits a
codominant mode of inheritance which is blood type AB

5. +
The ABO System
Genotype Antigen Phenotype
IA IA A
IA IO A
A
IB IB B
IB IO B
B
IA IB A and B AB
IO IO Neither O
LEGEND Allele Codes
IA Type A
IO Type O
IB Type B

6. +
What's the deal with "AB" blood?
Type AB is an example of
codominance. The IA allele & the IB allele
are "equal".

7. + Blood type is controlled by 3 alleles: A, B, O.
A & B are codominant, O is recessive.
a) What are the two genotypes possible for a
IA IA and IA IO
person who as A blood? ______________
b) What genotype does a person with AB blood
IA IB
have? _______________
c ) What genotype does a person with O blood
IO IO
have? _____________
d) What are the two genotypes possible for a
person who as B blood? ______________
IB IB and IB IO