Lea needs the Le gene.

Leb needs Le, Se gene. It doesn't need the H gene because Se froms an H antigen. Right?

If the H and Se genes are inherited: do the A, B and Le transferases compete for it ?

H gene is required! Without H, a person (hh) would be Bombay and not have the H chain produced and therefore regardless of what other genes are inherited, there would be no place for the antigens to form.

Bombay, Oh phenotypes, can produce Lea and Leb, if they inherit Le and Se.

If the H substance is present do the A, B (depending on the genes inhertied) and Le tranferases compete for the H antigen?

Lea needs the Le gene.

Leb needs Le, Se gene. It doesn't need the H gene because Se froms an H antigen. Right?

If the H and Se genes are inherited: do the A, B and Le transferases compete for it ?

Sorry Liz, I'm a bit confused by the question, but I'll do my best.

Lea certainly needs the LE (or FUT3) gene, but also needs the H (or FUT1 gene).

True Oh individuals are Le(a-b-). On the other hand, some "Oh" individuals do secrete Lewis substance, because they have the (FUT1 and FUT3 genes that make up the Type 1 backbone, but not the Type 2 that are integral to the red cell membrane).

This is much better explained by Geoff Daniels on pages 42-48 of his book Human Blood Groups (2nd edition) 2002, Blackwell Science. Geoff has a habit of explaining everything better than me!!!!!!!!!

In answer to your last question - yes. This is why the A and B antigens on red cells are weaker on the red cells of most AB individuals, than they are on A or B individuals (can prove this by titration). These, of course, are Type 2. In the case of Type 1, again, yes.

There is also a brilliant table/figure on page 342 of Rob Race and Ruth Sanger's book, Blood Groups in Man 6th edition, 1975, Blackwell Scientific Publications.

Ummmmmmmm, I hope that helps????????

The H antigen is defined by the terminal disaccharide, fucose α1→2 galactose. Two different fucosyltransferase (FUT) enzymes are capable of synthesizing the H antigen, FUT1 (H gene), and FUT2 (Secretor gene). FUT2 or Secretor recognizes type 1 chain pre- cursors to form type 1 chain H and Leb antigens. So Malcolm regarding Leb where does the H (FUT1) gene come in?

Let me answer my own question: genetically Oh individuals are homozygous for nonfunctional H (hh) and Secretor (sese ) genes, resulting in a complete absence of type 1 and type 2 chain H, A, B, and Leb antigens. Those individuals also type as either Le(a–b–) or Le(a+b–) caused by the absence of the Secretor (FUT2) gene. So Lea ican be formed, not Leb.

Quite!