Table 1.

Positions, sequences, and frequencies of MDR-1 variations

MDR-1 position, exon	Nucleotide sequence		Frequency, %				Region	Effect
	Wild type	mut	Analyzed individuals, N	Heterozygous	Homozygous	Homozygous calculated
1b/12	cgagTagcg	cgagCagcg	85	11.8	0	0.4	Exon 1	Noncoding
2/−1	tcggGatgg	tcggAatgg	188	11.2	0	0.4	Exon 2	TL initiation
2/61	gaacAataa	gaacGataa	188	17.6	0.5	0.81	Exon 2	Asn-Asp
5/−25	aatgGtatg	aatgTtatg	85	26	3.5	2.3	Intron
5/−35	aagaGacat	aagaCacat	85	1.2	0	0.01	Intron
5/307	agggTtctt	agggCtctt	85	1.2	0	0.01	Exon 5	Phe-Leu
6/+139	gcaaCaatg	gcaaTaatg	85	48.2	16.5	16.8	Intron	##
6/+145	atgtCgtgt	atgtTgtgt	85	2.4	0	0.01	Intron
11/1199	ttcaGttac	ttcaAttac	85	12.9	0	0.4	Exon 11	Ser-Asn
12/1236	agggCctga	agggTctga	188	48.9	13.3	14.4	Exon 12	Wobble ##
12/+44	cagtCacat	cagtTacat	188	11.7	0	0.4	Intron
17/−76	ttacTaatt	ttacAaatt	85	45.9	22.4	20.3	Intron
17/+137	gaagAtgta	gaagGtgta	85	1.2	0	0.01	Intron
26/3435	agatCgtga	agatTgtga	188	48.3	23.9	23	Exon 26	Wobble
26/3396	ttgcCtatg	ttgcTtatg	188	0.53	0	0.01	Exon 26	Wobble

The positions of the identified polymorphisms correspond to positions of the MDR-1 cDNA (GenBank accession no. M14758, codon TTC exon 10, F335, is missing in that sequence), with the first base of the ATG start codon set to 1. SNPs that are located in introns are presented as (exon+/−n), i.e., n nucleotides upstream (−) or downstream (+) of the exons that were defined by Chen et al. (4). Fifteen polymorphisms were identified. The number of samples that were included in the allele frequency determination is listed as (N). Homozygous calculated: the predicted ratios of the homozygous genotypes (q²) were calculated on the basis of the Hardy–Weinberg distribution, using the formulas p = (2 × AA + 1 × Aa)/2N and p + q = 1: AA = number of probands homozygous for the wild-type allele, Aa = number of heterozygotes, N = size of the sample test, p = frequency of the wild-type allele, q = frequency of the mut allele, q² = frequency of the genotype homozygous for the mut allele. # indicates polymorphisms that are linked.