UPSC Prelims 2001 Q136: Science & Technology – Biology
A man whose blood group is not known meets with a serious accident and needs blood
transfusion immediately. Which one of the blood groups mentioned below and readily available
in the hospital will be safe for transfusion?
- (a) O, Rh-
- (b) O, Rh+
- (c) AB, Rh-
- (d) AB, Rh+
Answer: (a) O, Rh-
Explanation
Safe blood group for emergency transfusion when the patient's group is unknown
| Blood group | Use |
|---|---|
| O Rh-negative | Universal donor — no A, B or Rh antigens on red cells |
| O Rh-positive | Has Rh antigen; risky for Rh-negative patients |
| AB Rh-positive | Universal recipient, not donor |
| AB Rh-negative | Has A and B antigens; unsafe for O, A or B patients |
A man whose blood group is not known meets with a serious accident and needs a blood transfusion immediately. Of the blood readily available in the hospital, the safe choice is O Rh-negative. They carry no A, B or Rh antigens, so the patient's antibodies have nothing to attack.
Answer: (a) O, Rh-.
Why each option is right or wrong
- (a) CORRECT. O Rh-negative is the universal donor.
- (b) Incorrect. Rh-positive blood can harm an Rh-negative patient.
- (c) Incorrect. AB blood carries A and B antigens.
- (d) Incorrect. AB Rh-positive is the universal recipient, not donor.
Key point
Karl Landsteiner discovered the ABO groups (Nobel 1930); about 90% of Indians are Rh-positive.
Remember
O Rh-negative = universal donor; AB Rh-positive = universal recipient.
Common mistakes
- Choosing AB+, the universal recipient.
- Forgetting the Rh factor and choosing O+.
- Mixing up universal donor and recipient.
Exam tip
Universal donor = no antigens = O negative.
Sources
- NCERT Class XI — Biology, chapter 'Body Fluids and Circulation' (blood groups)
- National Blood Transfusion Council — blood group compatibility