Blood groups

• Blood type

  Proteins on the surface of red blood cells
• Blood type phenotypes

  • A
  • B
  • AB
  • O
• Type A blood

  Has A antigens on the surface of red blood cells
• Type B blood

  Has B antigens on the surface of red blood cells
• Type AB blood

  Has both A and B antigens on the surface of red blood cells
• Type O blood

  Doesn't have A or B antigens on the surface of red blood cells
• If you have type B blood

  You can accept another person's type B blood because B is an antigen your body recognizes
• If you try to give a type A blood to a type B person

  Their immune system will attack it because A is an antigen they don't recognize
• Type O blood

  Can be donated to everyone
• Type O individuals

  Can only receive blood from another type O
• Type AB blood

  Can receive blood from anyone
• Rh factor

  A protein on the surface of red blood cells, can be positive or negative
• Determining blood type genotypes

  1. Homozygous A

  2. Heterozygous A

  3. Homozygous B

  4. Heterozygous B

  5. AB

  6. Homozygous O
• Blood type is genetically inherited and a great example of multiple alleles
• If parents both have type A blood

  They could have a baby with type O blood if they are both heterozygous A
• A DNA test would be needed to definitively determine if Baby Sylvester belongs to the parents
• Blood type


  Determined by the kinds of carbohydrate tags on the outside of red blood cells
• Antigens


  The tags on the outside of red blood cells
• Gene


  Encodes an enzyme responsible for building the antigens on the red blood cell membrane
• Alleles of the gene

  • ia allele
  • ib allele
  • little i allele
• ia allele


  Encodes an enzyme that builds type A antigens
• ib allele


  Encodes an enzyme that builds type B antigens
• little i allele


  Does not produce a functional enzyme, does not contribute to antigens
• Blood types


  • Type A
  • Type B
  • Type AB
  • Type O
• Determining blood type


  1. Genotype with 2 alleles

  2. ia allele is dominant to little i

  3. ib allele is dominant to little i

  4. ia and ib are codominant
• Type A blood has red blood cells with only type A antigens
• Type B blood has red blood cells with only type B antigens
• Type AB blood has red blood cells with both type A and type B antigens
• Type O blood has red blood cells without type A or type B antigens