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L Cavalli-Sforza

Publications and source records attributed to L Cavalli-Sforza.

12 recordsLinked to original sources
PubMed1991

A contiguous linkage map of chromosome 13q with 39 distinct loci separated on average by 5.1 centimorgans.

A fine-structure linkage map of chromosome 13q is presented. This map contains 39 continuously linked loci defined by genotypes generated from the CEPH family DNAs with 56 probe and enzyme combinations. An alpha-satellite probe for sequences on chromosome 13 was included, resulting in a complete map of 13q with 39 distinct loci. The map spans 1.715 M in males and 2.099 M in females and the mean genetic distance between adjacent loci is 5.1 cM. Although there was generally a several-fold excess of female recombination in the interstitial portion of 13q, an excess of recombination in males was observed at both ends of this chromosomal arm. This map should be useful for the localization of any additional marker, gene, or disease locus of interest on chromosome 13q.

Chromosome Mapping↗
PubMed1991

The study of variation in the human genome.

Regions of the genome showing high evolutionary stability are often conserved as a result of functional constraints. Conversely, more variable regions are likely to represent DNA with no functional or structural importance. However, as in the case of immunologically important regions, sequence divergence does not always indicate lack of functional importance. There is thus a wealth of information from both a functional and an evolutionary point of view that comes from studies of DNA sequence variation, a neglected aspect of the genome endeavor. Naturally, one cannot sequence hundreds of individuals in full, but a useful compromise is to use less expensive methods and to limit the more expensive types of analysis to an appropriately chosen sample of loci. The sample could be determined after careful consideration of categories of DNA segments with respect to individual variation. The study of such categories of DNA variation patterns can help in the understanding of the role of each gene and vice versa. One other important application requiring a study of DNA variation in different human populations is forensic DNA typing. This study requires a knowledge of allele frequencies in different human populations. Evidence of a match between two DNA samples is meaningless if the approximate population frequency of the DNA pattern is not known. It has been suggested (E. Lander) that one use the highest frequency for the most common allele as a baseline frequency estimate. Obviously, systems in which this is employed require an extensive analysis of population-specific allele frequencies. In general, the best way of studying interindividual variation when detecting or describing new polymorphisms is to include interethnic variation.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1986

Linkage of cystic fibrosis to two tightly linked DNA markers: joint report from a collaborative study.

A collaborative study involving seven research groups provided an opportunity to investigate the linkage relationships between cystic fibrosis and two DNA marker loci, MET and pJ3.11 (D7S8), on an extended sample of 211 tested families. The maximum lod scores, recombination estimates, and confidence upper bounds (in parentheses) were 91.0 at theta = .004 (.012) for CF and MET, 71.3 at theta = .003 (.011) for CF and D7S8, and 69.3 at theta = .018 (.036) for MET and D7S8. Three-locus analyses yielded best support for the order MET-CF-D7S8, with odds against the alternate orders CF-MET-D7S8 and CF-D7S8-MET of 9:1 and 161:1, respectively. However, the number of observed recombinants was small and only one of the recombinants was jointly informative for all three markers. Significant allelic association was found between CF and both MET and D7S8. Weaker association between the latter two loci is consistent with the order MET-CF-D7S8.

Alleles↗
PubMed1985

Genetic markers of an aboriginal Taiwanese population.

A group of Taiwan aborigines, the Toroko, was typed for 21 classical genetic loci. This is part of an ongoing program aimed at a comprehensive study of Taiwan aborigines. In this first paper a short summary of historical, archeological, and anthropological data in the literature is made, and results of the present survey are compared with older results from other aborigine tribes. An analysis of other neighboring populations from southeast Asia has also been carried out in order to give a preliminary answer to the question of origin of Taiwanese aborigines. Fifteen populations were studied for 13 loci by tree analysis, principal components, and isolation by distance. Tree analysis and principal component analysis gave results in fairly good agreement and indicate three major population clusters: a northeast cluster (Ainu, Korea, Japan, and Ryukyu); a southeast cluster (south China, Thailand, Vietnam, Philippines, Taiwan, and Toroko); and a third cluster including Malaya and Borneo. The positions of Polynesia, Micronesia, and Melanesia are somewhat peripheral. Analysis of the tree shows some potential cases of convergence, perhaps owing to admixture, and of divergence. The analysis of isolation by distance shows that geographic propinquity is a reasonably good predictor of general similarity in this area.

Humans↗
PubMed1983

Surnames in Sardinia. I. Fit of frequency distributions for neutral alleles and genetic population structure.

Distributions of surnames were examined using data from about 40 000 individuals from consanguineous marriages (1930-59) in the island of Sardinia. They fit the Karlin-McGregor (1967) distribution for neutral alleles. The logarithmic distribution by Fisher (1943) and the Karlin-McGregor (1967) distribution give practically indistinguishable fits to these data. The two parameters underlying the Fisher distribution, alpha and nu, are fully interdependent, given the sample size N. From the latter and from the number of surnames S, they can be easily and satisfactorily estimated. The quantity nu measures immigration to the area and can be taken as a measure of the richness of the gene pool, being closely related to the quantity theta = Nemu (Ne = effective population size, mu = mutation rate) after the necessary corrections have been taken care of. Surnames behave like genes transmitted by the male line. Differences of female and male migrations require correction for comparison with data from autosomal gene frequencies but there seem to be no important differences between female and male migration in this area, as judged by analysis of pedigrees of consanguineous marriages. It is probable that the migration estimates obtained in this material are lower than real ones, mostly because of a bias characteristic of the particular source of surnames here employed. The distribution of surnames from areas which have very recently undergone economic development is not at equilibrium and is not fitted as well as that of areas which have had less important recent changes. As might be expected, the disturbance is particularly marked in the class most sensitive to effects of recent increases in migration, that of rarest surnames (represented by only one individual). In fact in this material it is noticeable only in this class and correction can be made for it. At equilibrium of migration and drift, the number of surnames in a population sample of given size can give a complete description of the population structure for that sample, in the same sense that the number of alleles is a sufficient statistic for the study of neutral evolution. The study of surnames, given their nature of 'neutral' alleles, the large number of alleles and the ease with which large numbers of individual data can be collected, can be a valuable help in the study of genetic population structure.

Alleles↗
PubMed1978

Synthetic maps of human gene frequencies in Europeans.

Multivarate techniques can be used to condense the information for a large number of loci and alleles into one or a few synthetic variables. The geographic distribution of synthetic variables can be plotted by the same technique used in mapping the gene frequency of a single allele. Synthetic maps were constructed for Europe and the Near East, with the use of principal components to condense the information of 38 independent alleles from ten loci. The first principal component summarizes close to 30% of the total information and shows gradients. Maps thus constructed show clines in remarkable agreement with those expected on the basis of the spread of early farming in Europe, thus supporting the hypothesis that this spread was a demic spread rather than a cultural diffusion of farming technology.

Agriculture↗