title: Linkage disequilibrium analysis of the human adenosine deaminase (ada) gene provides evidence for a lack of correlation between hot spots of equal and unequal homologous recombination.
abstract: The linkage disequilibrium (LD) pattern within the adenosine deaminase (ADA) gene was analyzed by studying 13 polymorphic loci in 137 families from two European and three African populations. Evidence for the presence of a 12-kb meiotic crossover hot spot, spanning part of the first and the second intron and flanked by regions of reduced recombination activity, was obtained. Moreover, segregation analysis of 113 informative meioses revealed two recombination events that are internal or overlap the 12-kb region, thus suggesting a recombination rate for the hot-spot region about 50-fold higher than the mean rate across the human genome. Within the hot spot, a 144-bp palindromic sequence was also identified and its possible involvement in the recombination process is discussed. The 12-kb region characterized by the low degree of LD does not include the 3.2-kb region that is deleted, as a result of recurrent unequal homologous recombination between two Alu elements, in patients affected by autosomal severe combined immunodeficiency. This observation provides the first evidence for an absence of correlation between hot spots of equal and unequal homologous recombination.
authors.affiliation: Dipartimento di Genetica e Biologia Molecolare, Università La Sapienza, P.le Aldo Moro 5, 00185 Rome, Italy. fulvio.cruciani@uniroma1.it
authors.forename: Fulvio
authors.initials: F
authors.lastname: Cruciani
authors.forename: Laura
authors.initials: L
authors.lastname: Bernardini
authors.forename: Piero
authors.initials: P
authors.lastname: Santolamazza
authors.forename: David
authors.initials: D
authors.lastname: Modiano
authors.forename: Antonio
authors.initials: A
authors.lastname: Torroni
authors.forename: Rosaria
authors.initials: R
authors.lastname: Scozzari
mesh_terms: D000243:Adenosine Deaminase / Q000172:deficiency / Q000235:genetics*; D001483:Base Sequence; D017353:Gene Deletion; D005819:Genetic Markers; D014644:Genetic Variation; D006801:Humans; D007438:Introns; D015810:Linkage Disequilibrium; D008540:Meiosis; D018895:Microsatellite Repeats; D010375:Pedigree; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D016511:Severe Combined Immunodeficiency / Q000235:genetics
chemical_list: D005819:Genetic Markers; D000243:Adenosine Deaminase