Table 1.

Characteristics of P. falciparum var gene groups

var gene group	Upstream sequence	Position	Orientation (direction of transcription)	No. of genes in 3D7	No. of DBL domains	DBLα0/α1	No. of cysteines in amplified tag
A	UpsA	Subtelomeric	Telomeric	10	2–5	DBLα1	2
B/A	UpsB	Subtelomeric	Centromeric	4	4–7	DBLα1 or DBLα0a	2 or 4
B	UpsB	Subtelomeric	Centromeric	21	2–3	DBLα0	4
B/C	UpsB	Central	Telomeric	10	2–3	DBLα0	4
C	UpsC	Central	Telomeric	13	2–3	DBLα0	4

^aTwo of the 3D7 Group B/A var genes (PFL0020w and MAL6P1.4) have a DBLα0 domain and two (PF08_0140 and MAL6P1.316) have a hybrid DBLα0/α1 domain that is DBLα0-like at the N-terminus but DBLα1-like in the expressed sequence tag region (i.e. it has two rather than four conserved cysteine residues).