RT Journal Article SR Electronic T1 Linkage disequilibrium between four intragenic polymorphic microsatellites of the NF1 gene and its implications for genetic counselling. JF Journal of Medical Genetics JO J Med Genet FD BMJ Publishing Group Ltd SP 590 OP 593 DO 10.1136/jmg.33.7.590 VO 33 IS 7 A1 M C Valero A1 E Velasco A1 A Valero A1 F Moreno A1 C Hernández-Chico YR 1996 UL http://jmg.bmj.com/content/33/7/590.abstract AB Four intragenic polymorphic microsatellite markers, AAAT Alu repeat, IVS27AC28.4, ACI27.2, and IVS38GT53.0, located along a 65 kb DNA region of the NF1 gene, were used to genotype 64 Spanish families with neurofibromatosis type 1 (NF1). Linkage disequilirium between each pair of markers was evaluated. Three of these markers, AAAT Alu repeat, ACI27.2, and IVS38GT53.0, exhibit linkage disequilibrium between each other. Analysis of extended haplotypes provides further evidence of the disequilibrium within this region since only 11 haplotypes account for 52% of the total chromosomes. Because of linkage disequilibrium, the informativeness of marker combinations for genotyping of NF1 families is diminished. There was no difference in the overall distribution of alleles between affected and normal chromosomes. An at risk haplotype was not found, as expected for a disease with at least 50% of cases being sporadic.