Overview
This lecture explains the biological basis of human blood types, their genetic inheritance, importance in transfusions, and additional complexity from the Rh factor.
Blood Components and Antigens
- Red blood cells carry hemoglobin, which binds oxygen for transport in the body.
- Red blood cells also have surface proteins called antigens that help the immune system identify self-cells.
- The main antigens for blood typing are A and B.
Genetics of Blood Types
- Blood types are determined by three alleles: A, B, and O.
- Each person inherits one allele from each parent, making two alleles per individual.
- The A and B alleles are dominant, while the O allele is recessive.
- Type A results from AA or AO, type B from BB or BO, type AB from AB (codominance), and type O from OO.
Blood Type Compatibility and Transfusions
- Blood transfusion requires matching blood types to avoid immune rejection.
- People with type AB blood are universal recipients because they lack antibodies against A or B antigens.
- People with type O blood are universal donors because their blood lacks A and B antigens but they produce antibodies against both.
Rh Factor and Additional Blood Group Complexity
- The Rh factor refers to the presence (Rh+) or absence (Rh-) of the D antigen.
- Rh incompatibility can cause hemolytic disease in newborns if an Rh- mother carries an Rh+ fetus.
- Besides the ABO and Rh systems, there are other antigens complicating transfusions.
Cultural Beliefs and Evolution
- No scientific evidence supports a link between blood type and personality.
- Blood type distribution varies among populations, with unclear evolutionary reasons.
Comparison Across Species
- Other species have more blood types; for example, dogs have thirteen compared to humans' main four.
Key Terms & Definitions
- Antigen — Protein marker on cell surfaces that helps the immune system recognize self-cells.
- Allele — A variant form of a gene.
- Codominance — Genetic situation where both alleles are expressed equally.
- Rh factor — Another blood group antigen, positive when present, negative when absent.
- Hemolytic disease of the newborn — Condition where maternal antibodies attack fetal red blood cells.
Action Items / Next Steps
- Review blood type inheritance Punnett squares.
- Read about other less common blood group systems.