Multiple Alleles


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A very informative and comprehensive powerpoint on Multiple Alleles that I found while researching.

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Multiple Alleles

  1. 1. MULTIPLE ALLELES Genes which have more than two alleles © 2007 Paul Billiet ODWS
  2. 2. Genes and their alleles <ul><li>About 30% of the genes in humans are di-allelic , that is they exist in two forms, (they have two alleles) </li></ul><ul><li>About 70% are mono-allelic , they only exist in one form and they show no variation </li></ul><ul><li>A very few are poly-allelic having more than two forms </li></ul>© 2007 Paul Billiet ODWS
  3. 3. Combinations <ul><li>Di-allelic genes can generate 3 genotypes </li></ul><ul><li>Genes with 3 alleles can generate 6 genotypes (3+2+1) </li></ul><ul><li>Genes with 4 alleles can generate 10 genotypes </li></ul><ul><li>Genes with 8 alleles can generate 36 genotypes </li></ul>© 2007 Paul Billiet ODWS
  4. 4. Genes and the immune system <ul><li>Poly-allelic alleles are usually associated with tissue types </li></ul><ul><li>These genes are so varied that they provide us with our genetic finger print </li></ul><ul><li>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 ) </li></ul>© 2007 Paul Billiet ODWS
  5. 5. The ABO blood system <ul><li>This is a controlled by a tri-allelic gene </li></ul><ul><li>It can generate 6 genotypes </li></ul><ul><li>The alleles control the production of antigens on the surface of the red blood cells </li></ul><ul><li>Two of the alleles are codominant to one another and both are dominant over the third </li></ul><ul><li>Allele I A produces antigen A </li></ul><ul><li>Allele I B produces antigen B </li></ul><ul><li>Allele i produces no antigen </li></ul>© 2007 Paul Billiet ODWS
  6. 6. The ABO blood system <ul><li>Note: </li></ul><ul><li>Blood types A and B have two possible genotypes – homozygous and heterozygous. </li></ul><ul><li>Blood types AB and O only have one genotype each. </li></ul>© 2007 Paul Billiet ODWS O ii B I B i B I B I B A I A i AB I A I B A I A I A Phenotypes (Blood types) Genotypes
  7. 7. Blood types and transfusions <ul><li>Blood types vary and your immune system recognises your own blood type as being self </li></ul><ul><li>Other blood types are recognised as non-self </li></ul><ul><li>If a blood which is incompatible with your body is transfused it will result in the agglutination of the foreign red blood cells </li></ul>© 2007 Paul Billiet ODWS
  8. 8. Antigens © Biology Labs Online © Bioformatica
  9. 9. Agglutination © Dr Delphine Grézel, Ecole Nationale Vétérinaire de Lyon
  10. 10. Blood types and transfusions <ul><li>People who are Type A blood produce antibodies to agglutinate cells which carry Type B antigens They recognise them as non-self </li></ul><ul><li>The opposite is true for people who are Type B </li></ul><ul><li>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 </li></ul><ul><li>What about type AB people? </li></ul>© 2007 Paul Billiet ODWS
  11. 11. Donor-recipient compatibility <ul><li>Note: </li></ul><ul><li>Type O blood may be transfused into all the other types = the universal donor . </li></ul><ul><li>Type AB blood can receive blood from all the other blood types = the universal recipient . </li></ul>© 2007 Paul Billiet ODWS O AB B Donor A O AB B A Type Recipient = Safe transfusion = Agglutination