04MULTIPLE_ALLELES

7/29/2019 04MULTIPLE_ALLELES

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MULTIPLE

ALLELES

Genes which have more than two

alleles

2007 Paul Billiet ODWS
http://www.saburchill.com/IBbiology/bio_hp.htmlhttp://www.saburchill.com/IBbiology/bio_hp.html


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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



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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 36genotypes



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Genes and the immune

system

Poly-allelic alleles are usually associated

with tissue types

These genes are so varied that theyprovide us with our genetic finger print

This is very important to our immune

system which must tell the differencebetween our own cells (self) and invading

disease causing microbes (non-self)



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The ABO blood system

This is a controlled by a tri-allelic gene

It can generate 6 genotypes

The alleles control the production ofantigens onthe surface of the red blood cells

Two of the alleles are codominant to oneanother and both are dominant over the third

Allele IA produces antigen A

Allele IB produces antigen B

Allele i produces no antigen



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The ABO blood system

Genotypes Phenotypes (Blood types)IA IA AIA IB ABIAi AIB IB BIBi Bii O

Note:

Blood types A and B have two possible genotypes

homozygous and heterozygous.

Blood types AB and O only have one genotype each.



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Blood types and transfusions

Blood types vary and your immunesystem recognises your own blood typeas being self

Other blood types are recognised asnon-self

If a blood which is incompatible with your

body is transfused it will result in theagglutination of the foreign red bloodcells



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Antigens

Biology Labs Online

Bioformatica
http://www.occc.edu/trandall/biologylabs/Documents/Cells%20Membranes/Plasma_Membrane.htmhttp://bioinformatica.upf.edu/2005/projectes05/1.8/abstract.htmlhttp://bioinformatica.upf.edu/2005/projectes05/1.8/abstract.htmlhttp://www.occc.edu/trandall/biologylabs/Documents/Cells%20Membranes/Plasma_Membrane.htm


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Agglutination

Dr Delphine Grzel, Ecole Nationale Vtrinaire de Lyon
http://www2.vet-lyon.fr/ens/immuno/ENV_immuno_1A/immun1-04.htmhttp://www2.vet-lyon.fr/ens/immuno/ENV_immuno_1A/immun1-04.htmhttp://www2.vet-lyon.fr/ens/immuno/ENV_immuno_1A/immun1-04.htmhttp://www2.vet-lyon.fr/ens/immuno/ENV_immuno_1A/immun1-04.htmhttp://www2.vet-lyon.fr/ens/immuno/ENV_immuno_1A/immun1-04.htm


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Blood types and transfusions

People who are Type A blood produce antibodiesto agglutinate cells which carry Type B antigensThey 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 OType O cells do not carry any antigens for the ABO

systemType O cells pass incognito

What about type AB people?



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Donor-recipient compatibility

RecipientType A B AB O

ADonor B

ABO

= Agglutination= Safe transfusion

Note:

Type O blood may be transfused into allthe other types = the universal donor.

Type AB blood can receive blood fromall the other blood types = the universalrecipient.
