Multiple Alleles

• Multiple Alleles

  • When there are more than 2 alleles possible for one characteristic
  • These alleles can have different types of genetic relationships (dominance, co-dominance or incomplete dominance) depending on the combination of alleles

   
• Example one - ABO blood typing

  • There are 3 possible alleles which determine our blood type
  • These alleles are for A, B and O blood types
  • The alleles code for the presence or absence of proteins called antigens on the surface or erythrocytes
  • A person can have any 2 of the following three alleles: IA , IB or i
• • IA represents the presence of A antigens = A blood
  • IB represents the presence of B antigens = B blood
  • i represents no antigens present = O blood
  • IA   and IB are codominant and will both be expressed - AB blood
  • i is recessive to both IA and IB
• Why is ABO blood type important?

  It is crucial for blood transfusions to prevent agglutination and potential death.
• What are the surface antigens on erythrocytes?

  They are proteins that determine an individual's blood type.
• What are antibodies in the plasma of blood?

  They are proteins that detect and bond with incompatible blood types.
• What happens when antibodies bond with incompatible blood types?

  It causes the blood to clump or agglutinate.
• What is the role of macrophages in the context of agglutinated blood?

  They phagocytose the clumped blood to remove it from circulation.
• What type of antibodies do individuals with A blood have?

  Anti-B antibodies.
• What occurs if a person with A blood receives B blood?

  Their Anti-B antibodies will agglutinate the B blood.
• What are the consequences of agglutination in blood vessels?

  It can block blood vessels or decrease blood flow, potentially resulting in death.
• Why is it vital for doctors to check blood type before transfusions?

  To ensure that the blood type given does not react with the patient's antibodies.
• What are AB patients referred to as in terms of blood donation?

  Universal receivers.
• Why can AB patients receive blood from all other types?

  They have no antibodies against A or B antigens.
• What are O patients referred to as in terms of blood donation?

  Universal donors.
• Why can O patients donate blood to all other types?

  Their erythrocytes have no surface antigens.
• What is the limitation for O patients regarding blood transfusions?

  They can only receive blood from O donors.