Revision summary
Rh groups centre on the D antigen. Positive means D present; negative means D absent. An Rh-negative mother can be sensitised by an Rh-positive fetus. Anti-D prophylaxis prevents most haemolytic disease. Frequencies differ by population, as a polymorphism.
Model answer
Introduction
The Rh blood-group system is a set of red-cell antigens, of which D is the clinically decisive one. It matters in transfusion and in pregnancy.
Body
Genetics and types
- Landsteiner and Wiener named Rhesus after the monkey work; later mapping showed a human RH locus on chromosome 1.
- Rh positive means D is present. Rh negative means D is absent. C, c, E, e add further types.
- Inheritance is Mendelian. Population frequencies vary: Rh-negatives are commoner in some European groups than in many Indian samples.
Medical anthropology
- An Rh-negative mother and Rh-positive fetus can cause haemolytic disease of the newborn after sensitisation.
- Anti-D immunoglobulin prevents most cases. Transfusion must still match D.
- It is a polymorphism, not a racial essence.
Flow diagram
flowchart TD RH[Rh system] --> D[Antigen D] D --> POS[Rh positive] D --> NEG[Rh negative HDN risk]
Conclusion
Rh is a red-cell system led by antigen D. Its anthropological use is population frequency; its medical use is transfusion and HDN prevention.
Quick related
Students also ask
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Rhodesian Man
Next question in the 2016 paper (Q5). View answer →
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Is Rh the same as ABO?
No. They are different loci. Both must be matched in transfusion.
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Are all Indians Rh positive?
Most are D-positive, but Rh-negatives exist and need the same obstetric care.
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