SEARCH · PubMed Health

Results for “Lod Score”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources

PubMed1987

Dyslexia and chromosome 15 heteromorphism: negative lod score in a Danish material.

From a large Danish material of random families we selected families with dyslexia as reported by the families themselves and as recorded by a dyslexia institute. Among five "backcross families" studied for chromosome 15 polymorphisms we found only negative lod scores, and at theta = 0.10 a negative score of -3.42; i.e., in our material we did not find any confirmation of the indication of linkage between dyslexia and a chromosome 15 polymorphism found in part of their material by Smith et al. (1983, 1986).

Chromosomes, Human, Pair 15↗

PubMed1994

Another procedure for the preliminary ordering of loci based on two point lod scores.

Because of the difficulty of performing full likelihood analysis over multiple loci and the large numbers of possible orders, a number of methods have been proposed for quickly evaluating orders and, to a lesser extent, for generating good orders. A new method is proposed which uses a function which is moderately laborious to compute, the sum of lod scores between all pairs of loci. This function can be smoothly minimized by initially allowing the loci to be placed anywhere in space, and only subsequently constraining them to lie along a one-dimensional map. Application of this approach to sample data suggests that it has promise and might usefully be combined with other methods when loci need to be ordered.

Chromosome Mapping↗

PubMed1995

Two-locus maximum lod score analysis of a multifactorial trait: joint consideration of IDDM2 and IDDM4 with IDDM1 in type 1 diabetes.

To investigate the genetic component of multifactorial diseases such as type 1 (insulin-dependent) diabetes mellitus (IDDM), models involving the joint action of several disease loci are important. These models can give increased power to detect an effect and a greater understanding of etiological mechanisms. Here, we present an extension of the maximum lod score method of N. Risch, which allows the simultaneous detection and modeling of two unlinked disease loci. Genetic constraints on the identical-by-descent sharing probabilities, analogous to the "triangle" restrictions in the single-locus method, are derived, and the size and power of the test statistics are investigated. The method is applied to affected-sib-pair data, and the joint effects of IDDM1 (HLA) and IDDM2 (the INS VNTR) and of IDDM1 and IDDM4 (FGF3-linked) are assessed with relation to the development of IDDM. In the presence of genetic heterogeneity, there is seen to be a significant advantage in analyzing more than one locus simultaneously. Analysis of these families indicates that the effects at IDDM1 and IDDM2 are well described by a multiplicative genetic model, while those at IDDM1 and IDDM4 follow a heterogeneity model.

Diabetes Mellitus, Type 1↗

PubMed1990

Sample-size guidelines for linkage analysis of a dominant locus for a quantitative trait by the method of lod scores.

Sample-size guidelines for linkage studies of quantitative traits partially determined by a dominant major locus are needed to provide a rough estimate of the amount of pedigree material that should be sampled to map the loci that influence such traits. After pedigrees are sampled, a specific power calculation can be carried out to evaluate the linkage information provided by the sampled pedigrees. Using computer simulation, I provide sample-size guidelines for linkage studies by the method of lod scores of quantitative traits partially determined by a dominant major locus. I consider the effects of a trait model, marker characteristics, and sampling strategy, with particular attention to sampling strategy because it is the one factor which the investigator can fully control. My results suggest that linkage studies of quantitative traits are practical, particularly if the investigator chooses an efficient sampling design and an efficient strategy to select pedigrees for linkage analysis.

Female↗

PubMed1979

A lod score method for detecting linkage on the X chromosone between a marker locus and a major gene locus for a quantitative.

A sequential lod-score method is proposed for detecting linkage on the X chromosome between a marker locus and the locus of a major gene influencing a quantitative trait, The method uses information from sons of doubly heterozygous mothers. The average number of families required to detect linkage is substantially less than that of the fixed sample-size method proposed by Hill.

Female↗

PubMed1998

The quantitative LOD score: test statistic and sample size for exclusion and linkage of quantitative traits in human sibships.

We present a test statistic, the quantitative LOD (QLOD) score, for the testing of both linkage and exclusion of quantitative-trait loci in randomly selected human sibships. As with the traditional LOD score, the boundary values of 3, for linkage, and -2, for exclusion, can be used for the QLOD score. We investigated the sample sizes required for inferring exclusion and linkage, for various combinations of linked genetic variance, total heritability, recombination distance, and sibship size, using fixed-size sampling. The sample sizes required for both linkage and exclusion were not qualitatively different and depended on the percentage of variance being linked or excluded and on the total genetic variance. Information regarding linkage and exclusion in sibships larger than size 2 increased as approximately all possible pairs n(n-1)/2 up to sibships of size 6. Increasing the recombination (theta) distance between the marker and the trait loci reduced empirically the power for both linkage and exclusion, as a function of approximately (1-2theta)4.

Chromosome Mapping↗

PubMed1975

The use of lod scores for the determination of the order of loci on a chromosome.

A method is given for calculating the probabilities of the possible gene orders for a group of syntenic loci using lod scores calculated for each pair of loci in the group. Applying it, we find the most probable gene order for the five loci on chromosome 1 to be PGM1; Rh; PGD; PEP-C; Fy. However, the probabilities for other orders such that Rh lies between PGM1 and PGD with PEP-C and Fy outside these three are of a similar order of magnitude and no firm conclusions can be given. The probability for other possible orders is negligible.

Chromosome Mapping↗

PubMed1995