Which statement best describes the D antigen in Rh genetics?

Which statement best describes the D antigen in Rh genetics?

• A. It is present in the majority of individuals and defines Rh positive
• B. It is never present
• C. It is only present in certain races
• D. It is always expressed as D- negative

Answer: (A)

The D antigen on red blood cells is the most immunogenic part of the Rh system, and its presence defines Rh positive. When D is detected, the individual is labeled Rh positive; when D is absent, the individual is Rh negative. Because the D antigen is expressed by the majority of people across populations, Rh positive is more common. The other statements don’t fit because D antigen is not never present, not restricted to certain races, and Rh status is not described as always being D-negative—Rh negative simply means the D antigen is absent.

The D antigen on red blood cells is the most immunogenic part of the Rh system, and its presence defines Rh positive. When D is detected, the individual is labeled Rh positive; when D is absent, the individual is Rh negative. Because the D antigen is expressed by the majority of people across populations, Rh positive is more common. The other statements don’t fit because D antigen is not never present, not restricted to certain races, and Rh status is not described as always being D-negative—Rh negative simply means the D antigen is absent.