Fig. 1.— Surfactant protein (SP)-A2 and SP-A1 marker loci used in genotype analysis. The location of SP-A2 and SP-A1 genes relative to the centromere (C) and teleomere (T) is shown. The SP-A1 and SP-A2 genes are in opposite transcriptional orientation 10. The amino acid location of each bi-allelic SP-A2 and SP-A1 marker is shown on the bottom line, i.e. AA9 (the first A stands for SP-A and the second A for amino acid; the number denotes the actual amino acid). Above each amino acid location, the corresponding codon is shown and the single base polymorphism genotyped at each amino acid location is underlined in the corresponding codon. For SP-A2 alleles, bi-allelic markers at four amino acid locations (AA9, AA91, AA140 and AA223) are genotyped using converted polymerase chain reaction restriction fragment length polymorphism analysis. For example, allele 1A has the C polymorphism at all four amino acid locations. Each SP-A2 allele (1A, 1A0, 1A1, etc.) is determined by the combined pattern of the four bi-allelic markers, as shown. Similarly, for the SP-A1 alleles, bi-allelic markers at five amino acid locations (AA19, AA50, AA62, AA133 and AA219) are genotyped to determine SP-A1 alleles (6A, 6A2, etc.). C, A, G, T: nucleotide bases cytosine, adenine, guanine and thymine, respectively.