title: Family studies of lactase deficiency in the American Indian.
abstract: To determine the pattern of inheritance of lactase deficiency, we studied 104 American Indian and 2 white subjects in 19 families. Subjects were considered deficient in lactase if breath-hydrogen excretion exceeded 0.20 ml per min above fasting at 2 hr after a lactose load of 2 g per kg of body weight (maximum 50 g). Seventy-one per cent of the males and 75% of the females were lactase deficient. In three families in which both parents were lactase normal, 40% of the children were lactase deficient; and in the three families with one parent lactase normal and the other lactase deficient, 65% of the children were deficient in lactase; and finally, in the seven families with both parents lactase deficient, 93% of the children were lactase deficient. This distribution of lactase deficiency in the families suggests that this trait shows an autosomal-recessive pattern of inheritance.
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D005808:Genes, Recessive; D006801:Humans; D007198:Indians, North American; D007785:Lactose / Q000008:administration & dosage; D007787:Lactose Intolerance / Q000453:epidemiology / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D008910:Minnesota; D010375:Pedigree
chemical_list: D007785:Lactose