Q.In an accident there is great loss of blood and there is no time to analyse the blood group which blood can be safely transferred?

Alongside the ABO antigens, human red cells carry a separate antigen system, the Rh factor — specifically the 'D' antigen — discovered by Landsteiner and Wiener (1940) in rhesus monkey blood and soon after in humans. A person carrying the D antigen is Rh-positive; a person lacking it is Rh-negative. Unlike ABO antibodies, anti-D antibodies are not present naturally; an Rh-negative person only develops them after their immune system is actually exposed to Rh-positive blood.

Two genetic models explain Rh inheritance. The Fisher-Race hypothesis (in wider modern use) holds that Rh type is controlled by three closely linked gene pairs — C/c, D/d, E/e — at three adjacent loci on one chromosome; any genotype with at least one dominant D allele is Rh-positive, and only the double-recessive dd genotype is Rh-negative. The Wiener hypothesis instead proposes a single locus with eight possible alleles (R1, R2, R0, Rz, r, r1, r11, ry), where again a dominant 'R'-type …