Correct option is C
A. Galactose is added to the terminal of H-antigen by a transferase expressed in individuals with type A blood.(Incorrect)
- In individuals with type A blood, a specific glycosyltransferase enzyme (A-transferase) adds N-acetylgalactosamine (not galactose) to the H-antigen.
B. The B antigen is formed by a transferase expressed in individuals with type B blood, which adds a terminal N-acetylgalactosamine to H-antigen.(Incorrect)
- In individuals with type B blood, a specific glycosyltransferase enzyme (B-transferase) adds galactose (not N-acetylgalactosamine) to the H-antigen.
C. The H-antigen is formed by fucose transferase that adds a terminal fucose to its precursor.(Correct)
- The H-antigen is the foundation for the ABO blood group antigens and is produced when the fucosyltransferase enzyme (FUT1) adds fucose to the precursor.
D. The H-antigen is the precursor of both the A- and B-antigens, and it is the blood group antigen in persons of type O blood. (Correct)
- Type O individuals do not have functional A- or B-transferases, so they retain the H-antigen as their blood group marker.
- A- and B-antigens are derived from the H-antigen by specific transferases.
Information Booster:
- The ABO blood group system is determined by specific glycosyltransferase enzymes that modify the H-antigen.
- H-antigen is essential for A and B antigen formation; without it, no ABO blood type can develop.
- The FUT1 gene encodes the enzyme that synthesizes H-antigen, which is modified further to form A or B antigens.
- Type O blood lacks the enzymes to add extra sugars, leaving only the H-antigen on red blood cells.
- Bombay phenotype (hh) individuals lack the FUT1 enzyme, meaning they do not even have the H-antigen.
- Blood transfusion compatibility depends on the presence or absence of A, B, and H antigens.
