Biomedical subjects

Ida Malkin

Publications and source records attributed to Ida Malkin.

6 recordsLinked to original sources

PubMed2004

Sampling correction in linkage analysis.

In a linkage analysis that requires the estimation of parameters other than the recombination fraction, we can construct a pedigree likelihood that leads to consistent parameter estimators if the sampling procedures are known. In particular, it is necessary to identify the subset of pedigree members "relevant to sampling" (RS), where by sampling we mean both pedigree ascertainment through a proband combination and the selective inclusion of the sampled pedigrees in the data that are analyzed. If both these procedures are independent of the marker phenotypes and the model of trait inheritance is known, then no sampling or ascertainment correction is needed to obtain a consistent estimator of the recombination fraction. Otherwise, the correction can be of two types: sampling-model-based, in which the ascertainment and inclusion procedures are modeled and used in the likelihood expression, or sampling-model-free, in which the data RS are "conditioned out" without any modeling of the sampling procedures. In either case, the pedigree proband sampling frame must be identified.

Chromosome Mapping↗

PubMed2004

Lack of evidence for a major gene in the Mendelian transmission of BMI in Chinese.

OBJECTIVES: To determine the heritability of BMI and to examine the mode of inheritance of BMI variation in Chinese. RESEARCH METHODS AND PROCEDURES: Familial correlation and complex segregation analyses for BMI were undertaken in a Chinese sample composed of 392 nuclear families, with 1190 total individuals. RESULTS: A moderate heritability was found for BMI (h2 = 0.419-0.492). The obtained results do not support a major gene for BMI in our samples. BMI may be inherited in a complex and non-Mendelian manner in Chinese. DISCUSSION: The findings of this study suggest that identification of specific genes for BMI in Chinese, at least within the same data set, is a serious challenge because of the lack of evidence of a major gene for BMI in our Chinese sample.

Aged↗

PubMed2004

Israeli jewish infants of different descent: growth patterns, likeness and differences. Longitudinal study.

BACKGROUND: Due to increasing migration process and intermarriages among individuals belonging to different ethnic groups, it is important to examine whether intermixing of populations effects child growth rate. AIMS: To compare growth patterns of Jewish infants from distinct descent. SUBJECTS: 1300 Israeli children were divided into 7 groups: 4 groups of babies with both parents from the same geographic origin (Europe, Yemen, Middle East or North Africa) and 3 inter-mixed groups according to genetic distances between the parents' derivation. STUDY DESIGN: The studied infants were monitored longitudinally for both body length. weight and head circumference from birth until 20 months of life. Using the curve fitting technique the follow-up data were fitted to the 3-parameter Count model. OUTCOME MEASUREMENTS: Three sets of maximal likelihood estimates of the model parameters were obtained to test the growth patterns of different groups of Jewish children: individually-specific for every child, group specific for each individual within the group, and general for all individuals from all studied groups. Likelihood ratio test was used to examine whether the chosen function of trait dependence on age is uniformly reliable for all individuals from all the considered groups. RESULTS AND CONCLUSIONS: Significant differences were indicated between all studied growth curves for all three studied traits. Moreover, distances calculated between the studied cohorts demonstrated a clear distinction between the clusters of "non-mixed" and "mixed" groups for length and weight. Since the studied children were born and developed in similar environments, these results may serve as important evidence for the existence of a genetic effect on the growth process.

Body Height↗

PubMed2003

Cortical index and size of hand bones: segregation analysis and linkage with the 11q12-13 segment.

BACKGROUND: Bone geometry (BG) and size (BS) are important factors in determining bone fragility. Previous studies have suggested that more than half of BG and BS variation is genetically determined. The possible chromosomal locations of genes involved in BS and BG determination have not been explored. We evaluated the extent and mode of inheritance of the radiographic hand BS index (BSI) and the metacarpal cortical index (MCI), and tested the hypothesis of linkage between these traits and the 11q 12-13 chromosomal region. MATERIAL/METHODS: Hand radiographs and blood samples were collected from 1190 individuals belonging to 349 Chuvasha nuclear families (Russian Federation). Segregation analysis was conducted on a total sample. Transmission disequilibrium testing (TDT) and model-based linkage analyses (MBLA) were performed on a sub-sample of 163 families. RESULTS: The hypothesis of a major gene effect was confirmed for both studied traits. The best-fitting models were Mendelian, with an additive type of inheritance. The inferred major gene explained 50% of the CI and 40% of the BSI variation. The TDT and MBLA results did not permit confirmation of hypotheses about linkage between hand BSI and the 11q 12-13 chromosomal region, but a possible linkage between CI and that region cannot be ruled out. CONCLUSIONS: We support the hypothesis of a major gene effect in the heritability of BSI and MCI. We provide suggestive evidence for possible linkage disequilibrium between MCI and the 11q12-13 chromosomal segment (marker D11S1983), but not for a linkage between BSI and this

Adolescent↗

PubMed2003

Complex segregation analysis of body height, weight and BMI in pedigree data from Middle Dalmatia, Croatia.

It has recently been reported that the mode of inheritance of body height, weight and BMI in five ethnically and geographically different populations can be described in terms of a major gene (MG) model. Here, using the pedigree sample from the island populations of Middle Dalmatia, Croatia (1,312 observed individuals in 462 pedigrees), the evidence is presented that supports the above findings. By applying the usual transmission probability tests, the hypothesis has been accepted that a significant part of the variation of each one of those three basic morphological traits can be attributed to the effect of a putative large-effect gene. The effect of a putative MG is responsible for 39-50% of age and sex adjusted trait's variation and for 34-48% of the total (non age-adjusted) variation of height, weight and BMI.

Adolescent↗

PubMed2002

Increase in power of transmission-disequilibrium tests for quantitative traits.

Allison ([1997] Am. J. Hum. Genet. 60:676-690) proposed four versions of the transmission-disequilibrium test (TDT) for quantitative traits when there is extreme-threshold sampling, i.e., the trios having an offspring trait value between a priori defined thresholds are excluded from the analysis. Keeping intact the ideology and construction of these tests, we propose here an extreme-offspring design for the trios: for each parent pair of which at least one is heterozygous at a marker locus, the offspring having the most extreme trait value is selected for the trio. Our simulation studies show that the effect of the extreme-offspring design can be quite substantial (up to 30% increase in test power), and that the increase is greater for smaller values of the association parameter and for traits with smaller heritability: just those cases where the increase in power is especially desirable.

Data Interpretation, Statistical↗