PubMed Health⌕ Search

Biomedical subjects

I Balazs

Publications and source records attributed to I Balazs.

At least 19 recordsLinked to original sources
PubMed1992

Forensic applications.

The introduction of DNA based identity testing has revolutionized the field of forensic analysis of biological materials. Most of the publications during the past year expand earlier studies that began more than seven years ago, on the properties of DNA recovered from different types of evidential materials; these studies examine the suitability of these samples for identity testing, the effect of different environmental insults the population genetics of loci used for identity testing, and the methods used for statistical analysis of the DNA patterns.

DNA Probes↗
PubMed1992

Human population genetic studies using hypervariable loci. I. Analysis of Assamese, Australian, Cambodian, Caucasian, Chinese and Melanesian populations.

Population genetic studies, in Australian, Assamese, Cambodian, Chinese, Caucasian and Melanesian populations, were performed with several highly polymorphic DNA loci. Results showed that the Caucasian and Chinese had the highest level of heterozygosity. The size range of the majority of the polymorphic DNA fragments of a locus was the same in the different populations. The distinguishing feature of each ethnic group was the relative frequency of a particular set or group of alleles. For example, alleles greater than 9.0 kb in size, in D14S13, or from 4.5 to 4.7 kb, in D18S27, were less than half as frequent in Caucasians than in the other populations. Overall, there were groups of alleles, at one or more loci, whose frequencies were different among some of the ethnic groups and therefore could be used to differentiate one group from the other.

Alleles↗
PubMed1992

Genetic and physical mapping on chromosome 4 narrows the localization of the gene for facioscapulohumeral muscular dystrophy (FSHD).

We have used a combination of classical RFLPs and PCR-based polymorphisms including CA repeats and single-strand conformation polymorphisms to generate a fine-structure genetic map of the distal long arm of chromosome 4q. This map is now genetically linked to the pre-existing anchor map of 4pter-4q31 and generates, for the first time, a complete linkage map of this chromosome. The map consists of 32 anchor loci placed with odds of greater than 1,000:1. The high-resolution map in the cytogenetic region surrounding 4q35 provides the order 4cen-D4S171-F11-D4S187-D4S163-D4S139-4q ter. When we used somatic cell hybrids from a t(X;4)(p21;q35) translocation, these five markers fell into three groups consistent with the genetic map-D4S171 and F11 in 4pter-4q35, D4S163 and D4S139 in 4q35-4qter, and D4S187 as a junction fragment between these two regions. These markers are in tight linkage to the gene for facioscapulo-humeral muscular dystrophy (FSHD) mapped to this region by several collaborating investigators and provide a framework for further detailed analysis of this region.

Base Sequence↗
PubMed1991

Studies of three Amerindian populations using nuclear DNA polymorphisms.

Three Amerindian populations, two from Rondônia, Brazil (Karitiana and Rondônia Suruí), and one from Campeche, Mexico (Mayan), were typed for up to 30 nuclear restriction fragment length polymorphisms (RFLPs). Heterozygosities, both observed and expected, were compared with those of Europeans. Average heterozygosity is reduced among these Amerindians (relative to that of Europeans) by 7.0% (Mayan) to 27.1% (Karitiana). This amount of heterozygosity in the nuclear DNA is nevertheless high enough that it is unlikely that there was a severe or prolonged bottleneck.

Alleles↗
PubMed1990

DNA linkage analysis and studies of the androgen receptor gene in a large kindred with complete androgen insensitivity.

DNA linkage analysis of the X chromosome and studies with cDNA probes specific for the androgen receptor gene were performed on the largest known kindred with the syndrome of complete androgen insensitivity. The affected subjects (XY) have absent binding of dihydrotestosterone to the androgen receptor (the receptor negative form of androgen insensitivity). In this kindred there was maternal transmission of the gene, with all affected males expressing complete genital feminization. Linkage analysis studies were conducted with two DNA probes, DXS1 and PGK1, localized to the Xq11-Xq13 region of the long arm of the X chromosome near the centromere. The results demonstrate linkage to the markers in the order of DXS1-(AR; PGK1), thus localizing the AR gene to an area between Xq11 and Xq13. Three cDNA probes that span various parts of the androgen receptor gene, including the DNA and steroid binding domain, were used to evaluate the androgen receptor gene in normal individuals, carrier mothers, and affected subjects. Identical restriction fragment patterns were found in all three groups studied. Thus the androgen receptor gene was present in affected subjects without detectable DNA polymorphism at the androgen binding domain. Therefore, despite complete absence of binding to the androgen receptor, the defect in the androgen receptor gene in this kindred is not the result of a gene deletion. The results point to a mutation or a small insertion/deletion as the probable cause of the syndrome.

Cell Line↗
PubMed1990

Increased migration rate observed in DNA from evidentiary material precludes the use of sample mixing to resolve forensic cases of identity.

The analysis of restriction fragment length polymorphisms in forensic DNA samples can be used to determine whether any two or more samples have the same biological origin. However, sometimes DNA recovered from evidentiary material, such as blood or semen stains, migrates at a different rate than an exemplar sample. This difference in migration, while maintaining the same overall pattern, produces a shift in the position of the bands. To verify that a shift in migration has occurred between evidence and exemplar samples, we have utilized two DNA probes that recognize DNA fragments that do not vary in size between individuals (monomorphic). The results obtained with this type of internal control show that differences in migration rate between exemplar and evidentiary samples can be recognized and accounted for and do not affect the ability to decide whether two patterns match. A common practice in many analytical tests, to show identity between two samples, is to test the properties of the samples individually and mixed. However, this approach is not applicable to all forensic DNA identity tests. In many cases, DNA from forensic samples may be irreversibly modified and this can alter the migration rate of the DNA samples. Thus, in a mixture of DNA from exemplar and evidence, the same polymorphic DNA fragments may not comigrate and produce a composite pattern which could lead to false exclusions.

DNA↗
PubMed1989

Human population genetic studies of five hypervariable DNA loci.

Population genetic studies were performed using DNA probes that recognize five hypervariable loci (D2S44, D14S1, D14S13, D17S79, and DXYS14) in the human genome. DNA from approximately 900 unrelated individuals, subdivided into three ethnic groups (American blacks, Caucasians, and Hispanics) were digested with PstI and were successively hybridized to each DNA probe. The number of distinct DNA fragments identified for each of these regions varies from 30 to more than 80. An allele frequency distribution was determined for each locus and each ethnic group. The results show significant differences, between ethnic groups, in the pattern of distribution as well as in the relative frequency of the most common alleles of D2S44, D14S1, and D14S13 but only small differences in others (i.e., D17S79 and DXYS14). The results presented show that the analysis of these loci can have useful applications in population genetics as well as in identity tests.

Alleles↗
PubMed1989

Evaluation of deoxyribonucleic acid (DNA) isolated from human bloodstains exposed to ultraviolet light, heat, humidity, and soil contamination.

This study was designed to analyze the effects of common environmental insults on the ability to obtain deoxyribonucleic acid (DNA) restriction fragment-length polymorphisms (RFLP) patterns from laboratory prepared specimens. The environmental conditions studied include the exposure of dried bloodstains to varying amounts of relative humidity (0, 33, 67, and 98%), heat (37 degrees C), and ultraviolet light for periods of up to five days. In addition, the effect of drying over a four-day period in whole blood collected with and without ethylenediaminetetraacetate (EDTA) was examined. The results of the study showed that, under the conditions studied, the integrity of DNA is not altered such that false RFLP patterns are obtained. The only effect observed was that the overall RFLP pattern becomes weaker, but individual RFLP fragments are neither created nor destroyed.

Blood Stains↗
PubMed1989

The effects of environment and substrata on deoxyribonucleic acid (DNA): the use of casework samples from New York City.

This study was designed to analyze the effects of the environment and substrata on the quality of deoxyribonucleic acid (DNA) isolated from evidentiary specimens. The quality of DNA isolated from actual casework specimens was determined by measuring its size by agarose gel electrophoresis. The information obtained could be used to predict the suitability of the DNA in the samples for restriction fragment length polymorphism (RFLP) analysis. The evidentiary specimens chosen for DNA were classified according to substrate (scrapings, plastic bags, synthetics, denim, and carpet) and according to a subjective evaluation of the condition of the stain (soiled, damp, or putrefied) and to its size (small or large). The results show that DNA of sufficient quality and high molecular weight (HMW) can be reliably isolated from bloodstains deposited on evidentiary items which have an unknown environmental history and which have dried onto a variety of substrata. Subsequent RFLP analysis of a selected number of these samples verified that the DNA was suitable for this type of analysis.

Blood Stains↗
PubMed1986

The cellular homologue of the transforming gene of SKV avian retrovirus maps to human chromosome region 1q22----q24.

We report the chromosomal localization of the cellular oncogene SKI, the putative oncogene of the Sloan-Kettering viruses (SKVs), a group of transforming retroviruses that had been isolated from chicken embryo cells infected with the avian leukosis virus tdB77. Southern blot analysis of DNA from mouse X human somatic cell hybrids with the v-SKI probe established synteny with chromosome 1, but excluding the region 1pter----q21. In situ hybridization of the same probe both to human spermatocyte pachytene and lymphocyte metaphase chromosomes enabled precise localization of the gene to the region 1q22----q24, a region that frequently is involved in translocations and other rearrangements in diverse human tumor types. In situ hybridization studies of metaphase spreads from a small noncleaved cell lymphoma that exhibited a t(1;14)(q21;q32) translocation showed that SKI translocates to the der(14) chromosome. Cytogenetic analysis of 65 prospectively ascertained non-Hodgkin's lymphomas revealed that the SKI region undergoes nonrandom breakage leading to translocations. Further analysis of the chromosome breaks in this group of lymphomas suggested that those involving the SKI site probably are of importance in tumor progression.

Animals↗
PubMed1986

Allele frequency distribution of two highly polymorphic DNA sequences in three ethnic groups and its application to the determination of paternity.

The allele frequency distribution of two highly polymorphic DNA sequences has been determined in three ethnic groups (American blacks, Caucasoids, and Hispanics) from the New York metropolitan area. The two loci examined were D14S1 and the flanking region of HRAS-1. The former was analyzed in EcoRI-digested DNA and the latter in TaqI-digested DNA. Approximately 700 DNA samples from unrelated individuals were digested with each of these enzymes and hybridized with the appropriate recombinant DNA probes. The size range of the DNA fragments detected for the D14S1 polymorphism varied from 14.3 to 32.5 kilobase pairs (kbp). The number of alleles identified under the experimental conditions used in this study was more than 40. For the HRAS-1 polymorphism, we have detected 18 different alleles varying in size from 1.85 to 4.5 kbp. Although the number of alleles observed in the different ethnic groups examined was very similar, the relative frequency of them varied significantly. The results presented here can be used as the basis for the utilization of DNA RFLP for the purpose of identity, such as paternity determinations or the analysis of forensic material. As an example, we have compared the results of paternity cases analyzed by HLA typing with those obtained with these two DNA polymorphisms. The values of paternity index and power of exclusion were similar by both procedures.

Alleles↗
PubMed1986

Analysis of restriction fragment length polymorphisms in deoxyribonucleic acid (DNA) recovered from dried bloodstains.

Deoxyribonucleic acid (DNA) was recovered from dried bloodstains aged up to three years and shown to be of high molecular weight. DNA was digested with restriction endonucleases and fractionated by agarose gel electrophoresis. Following transfer to a filter, DNA was hybridized with two different radioactively labeled recombinant probes which recognize highly polymorphic regions in human DNA. The autoradiographic pattern observed was not altered by sample age, and the size of the alleles was consistent with those observed in the general population. Therefore, DNA of high molecular weight prepared from dried blood samples can be used for identification.

Base Sequence↗
PubMed1986

Application of deoxyribonucleic acid (DNA) polymorphisms to the analysis of DNA recovered from sperm.

Sperms, collected following sexual activity of volunteers, were processed to isolate high-molecular weight deoxyribonucleic acid (DNA). These DNA samples were digested with particular restriction endonucleases and analyzed with probes that recognize polymorphic DNA regions within the human genome. The pattern of restriction fragment length polymorphisms (RFLP) detected by this test is identical to that observed with DNA prepared from blood of the male sexual partner. Therefore, RFLP analysis can be used to exclude or to determine the probable identity of an assailant in rape cases.

Base Sequence↗