multiple alleles, recepient donor combinatons alleles characteristics and combinatorial interactions.

1. MULTIPLE
ALLELES
Genes which have more than two
alleles
© 2007 Paul Billiet ODWS

2. Genes and their alleles
 About 30% of the genes in humans
are di-allelic, that is they exist in two
forms, (they have two alleles)
 About 70% are mono-allelic, they
only exist in one form and they show
no variation
 A very few are poly-allelic having
more than two forms
© 2007 Paul Billiet ODWS

3. Combinations
 Di-allelic genes can generate 3 genotypes
 Genes with 3 alleles can generate 6
genotypes (3+2+1)
 Genes with 4 alleles can generate 10
genotypes
 Genes with 8 alleles can generate 36
genotypes
© 2007 Paul Billiet ODWS

4. Genes and the immune
system
 Poly-allelic alleles are usually associated
with tissue types
 These genes are so varied that they
provide us with our genetic finger print
 This is very important to our immune
system which must tell the difference
between our own cells (self) and invading
disease causing microbes (non-self)
© 2007 Paul Billiet ODWS

5. The ABO blood system
 This is a controlled by a tri-allelic gene
 It can generate 6 genotypes
 The alleles control the production of antigens on
the surface of the red blood cells
 Two of the alleles are codominant to one
another and both are dominant over the third
 Allele IA produces antigen A
 Allele IB produces antigen B
 Allele i produces no antigen
© 2007 Paul Billiet ODWS

6. The ABO blood system
Genotypes Phenotypes (Blood types)
IA IA A
IA IB AB
IAi A
IB IB B
IBi B
ii O
Note:
 Blood types A and B have two possible genotypes –
homozygous and heterozygous.
 Blood types AB and O only have one genotype each.
© 2007 Paul Billiet ODWS

7. Blood types and transfusions
 Blood types vary and your immune
system recognises your own blood type
as being self
 Other blood types are recognised as
non-self
 If a blood which is incompatible with your
body is transfused it will result in the
agglutination of the foreign red blood
cells
© 2007 Paul Billiet ODWS

8. Antigens
© Biology Labs Online
© Bioformatica

9. Agglutination
© Dr Delphine Grézel, Ecole Nationale Vétérinaire de Lyon

10. Blood types and transfusions
 People who are Type A blood produce antibodies
to agglutinate cells which carry Type B antigens
They recognise them as non-self
 The opposite is true for people who are Type B
 Neither of these people will agglutinate blood cells
which are Type O
Type O cells do not carry any antigens for the ABO
system
Type O cells pass incognito
 What about type AB people?
© 2007 Paul Billiet ODWS

11. Donor-recipient compatibility
Recipient
Type A B AB O
A
Donor B
AB
O
= Agglutination
= Safe transfusion
Note:
 Type O blood may be transfused into all
the other types = the universal donor.
 Type AB blood can receive blood from
all the other blood types = the universal
recipient.
© 2007 Paul Billiet ODWS