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PubMed1985

Genetic screening for hemophilia A (classic hemophilia) with a polymorphic DNA probe.

We have developed a new method of screening for hemophilia A in families at risk for the disease. A DNA probe (St14) that detects a very polymorphic region on the human X chromosome has been shown to be closely linked to hemophilia A. We observed no recombination between the St14 locus and hemophilia A in 12 families studied. The odds in favor of linkage are 4.4 X 10(9) to 1 (lod score, 9.65). The 95 per cent confidence interval for the probability of a recombination between St14 and hemophilia A is 0 to 6.5 per cent. This DNA probe, which is informative in more than 90 per cent of families at risk of hemophilia A, can be used in conjunction with classic biologic assays to identify carriers with an accuracy of 96 per cent or more. If a small risk of misclassification due to crossover between the test and the disease loci is accepted, this DNA marker should allow first-trimester prenatal diagnosis of hemophilia A. Segregation analysis with St14 may thus represent a major improvement in genetic counseling for hemophilia A.

Alleles↗
PubMed2005

Pilot study of arbitrarily primed PCR-single stranded DNA conformation polymorphism analysis for screening genetic polymorphisms related to specific phenotypes.

BACKGROUND: To investigate relationships between phenotypes and genotypes is not simple. We propose a phenotype-to-genotype screening strategy and pooled DNA system. As a pilot study of this strategy, we used arbitrarily primed polymerase chain reaction (AP-PCR) in combination with single-stranded DNA conformation polymorphism (SSCP) to screen for genetic polymorphisms associated with longevity. METHODS: Study subjects were separated into 3 age groups, individuals aged >100 years, 90-99 years and 60-69 years. Genomic DNAs were prepared from each individual, pooled to represent the 5 study groups, and then the pooled genomic DNAs were subjected to AP-PCR-SSCP analysis. RESULTS: We found 1 SNP more frequently in senior citizens with longevity. The genotype frequency of the 82133G>A polymorphism of human chromosome 3 clone RP11-61K12 (AC011199) differed significantly (P=0.0189, Fisher's exact test) between older subjects (>90 years) and younger subjects (<70 years). It is noteworthy that the strategy we describe herein was useful for identifying an SNP that showed statistically significant differences in its distribution across the subject groups. CONCLUSIONS: The pooled DNA strategy and quantitative genotype discrimination can also be applied to screening for the relationship between phenotype and genotype more effectively.

Adult↗
PubMed1977

Knowledge about and attitudes toward genetic screening among high-school students: the Tay-Sachs experience.

High school students (ages 15 to 18 years; No. = 930) taking biology in their curriculum were surveyed (the first survey), in the classroom, for their knowledge and attitudes about Tay-Sachs disease and other "public" issues in genetics. High-school students now constitute 38.9% of those screened for the Tay-Sachs gene in the Montreal program and the participation rate is 75% among eligible Jewish students. Knowledge and attitudes about the screening experience were also surveyed (the second survey) in a sample (No. = 120) containing equal numbers of carriers and noncarriers matched for sex and age. The response rate was 75% in the second survey. The first survey revealed that the level of knowledge about Tay-Sachs disease is high among students, only 28% percent of whom were Jewish. Students have a very positive attitude toward genetic screening in general. These findings are associated with an effort to expand the human genetics content in the biology curriculum. The second survey revealed a favorable attitude toward the screening experience and the self-knowledge obtained among screened students. The screening clinic in the schools, and literature provided by the screening authority, was an effective source of knowledge about the significance of Tay-Sachs heterozygosity. Carriers experienced initial anxiety; later attitudes were similar in carrier and noncarriers. Self-image was unchanged in 90% and diminished in 10% of carriers and enhanced in 10% of noncarriers. Heterozygous students perceive information about their genetic status as useful to themselves and 95% want to know the gennotype of an intended spouse; 88.4% would marry a carrier and only 11.6% would "reconsider." These findings encourage us to emphasise high-school screening as the preferred program in our community and to offer it as an effective aid to the physician faced with increasing demands in medical genetics. It is also an effective model for teaching some genetics and human biology in the schools.

Adolescent↗
PubMed1995

Genetic screens to identify elements of the decapentaplegic signaling pathway in Drosophila.

Pathways for regulation of signaling by transforming growth factor-beta family members are poorly understood at present. The best genetically characterized member of this family is encoded by the Drosophila gene decapentaplegic (dpp), which is required for multiple events during fly development. We describe here the results of screens for genes required to maximize dpp signaling during embryonic dorsal-ventral patterning. Screens for genetic interactions in the zygote have identified an allele of tolloid, as well as two novel alleles of screw, a gene recently shown to encode another bone morphogenetic protein-like polypeptide. Both genes are required for patterning the dorsalmost tissues of the embryo. Screens for dpp interactions with maternally expressed genes have identified loss of function mutations in Mothers against dpp and Medea. These mutations are homozygous pupal lethal, engendering gut defects and severely reduced imaginal disks, reminiscent of dpp mutant phenotypes arising during other dpp-dependent developmental events. Genetic interaction phenotypes are consistent with reduction of dpp activity in the early embryo and in the imaginal disks. We propose that the novel screw mutations identified here titrate out some component(s) of the dpp signaling pathway. We propose that Mad and Medea encode rate-limiting components integral to dpp pathways throughout development.

Alleles↗
PubMed1994

HIV type 1 variation in World Health Organization-sponsored vaccine evaluation sites: genetic screening, sequence analysis, and preliminary biological characterization of selected viral strains. WHO Network for HIV Isolation and Characterization.

A laboratory network has been established by the World Health Organization (WHO) to systematically isolate and characterize HIV strains from different parts of the world, and to obtain information and reagents that would facilitate HIV vaccine development. Sixty-three HIV-1 isolates obtained from 224 specimens collected during 1992-1993 in Brazil, Rwanda, Thailand, and Uganda were characterized in this initial study. Virus strains were first genetically subtyped using three different screening methodologies: PCR-gag fingerprinting, RNase A mismatch, and heteroduplex mobility assay (HMA). In addition, selected viruses were sequenced in V3 (52 strains), C2-V3 (42 strains), gp120 (15 strains), and/or gp160 (8 strains) regions of their envelope genes. These studies identified viruses belonging to different sequence subtypes in the four countries: 16 subtype B and 1 subtype C strains in Brazil, 13 subtype A strains in Rwanda, 15 subtype E and 2 subtype B strains in Thailand, and 3 subtype A and 13 subtype D strains in Uganda. Comparison of sequence data with results from the genetic screening efforts identified the HMA as a rapid and reliable method for sequence subtype determinations. The majority of strains were collected from persons documented to have recently seroconverted to HIV-1 positivity, and most strains were found to have slow replication and low cytopathic characteristics and to be non-syncytium-inducing (slow/low-NSI phenotypes) in vitro, which, in many cases, correlated with the corresponding genotype and charge of the V3 loop amino acid sequences. This collection of HIV strains is presently being characterized immunologically and serologically, including neutralization assays, to define whether there are immunological correlates of the sequence subtypes. Identification of potential immunotypes would be of considerable importance for the further development of HIV vaccines.

AIDS Vaccines↗
PubMed2001

[Genetic screening of meiotic mutations in mosaic clones of the Drosophila melanogaster female germline].

A method of screening for meiotic mutations based on genetic analysis of chromosome disjunction in germline mosaic clones of females homozygous for potential mutations is proposed. The clones are obtained at high frequency due to the use of the transgenic FLP/FRT system of mitotic recombination. This system permits obtaining homozygous clones in the first generation after mutagenesis, whereas the cultures are set up after selection for potential meiotic mutations. This significantly enhances, the efficiency of screening by the elimination of the limiting stage. Using this method, the following mutations were revealed in the 3L arm of Drosophila: ff6 leading to disturbed centriole disjunction, which results in appearance of multi-tail spermatids and three-pole spindles during male meiosis; ff3 leading to the formation of chromosome bridges in anaphase and telophase, chromosome nondisjunction, and premature chromatin condensation after metaphase; embryonic lethal ff29, with disturbed coordination between nuclear and centrosome cycles during syncytial cleavage; and a series of other mutations causing a wide spectrum of disturbances in male meiosis. Comparison of the proposed method with procedures of screening for yeast cell-cycle mutations showed that we succeeded in attaining the efficiency of screening in the Drosophila model close to that in the yeast model.

Animals↗
PubMed1996

Genetic screening, testing and treatment: how far can we go?

Treatment comes in three forms: care, control, cure; each will be part of any new development in the management of genetic disease, either Mendelian or complex. Diagnosis recognizes three states of disease: impairment, disability, and handicap when the disease is symptomatic and has manifestations. Genetics in health care has the potential to prevent these manifestations by interventions at the presymptomatic stage. Wherever cause of disease involves genotypic variation that undermines homeostasis, genetic testing and screening could play a predictive role. The area of greatest interest will be the common multifactorial diseases. While some persons worry that geneticists have taken society too fast and far along the road to ruin, it is closer to the truth that we have actually gone rather slowly and not very far along the road to better personal and collective health. With wisdom and caution the new opportunities for genetic testing or screening will become part of health care; and sooner rather than later when better treatments for our inherited infirmities are found.

Genetic Diseases, Inborn↗
PubMed1988

Ethical issues in genetic screening for susceptibility to chronic lung disease.

The extent, severity, and irreversible nature of chronic lung disorders associated with occupation dictate careful review of any potentially mitigating measure. A genetic predisposition to lung injury is known to occur in the small percentage of individuals who are homozygous for alpha-1-antitrypsin (AAT) deficiency, a defect in the protein needed for inactivating proteolytic enzymes released after lung injury. It was found that the contribution of homozygous affected individuals to the total population at risk for chronic lung disease is too small (0.5% to 2.0%) to warrant screening. Screening could be justified if the more prevalent heterozygous AAT-deficient individuals were also at greater risk. A literature review demonstrated that up to 27.2% of persons of Spanish and 12.3% of Anglo-Saxon heritage but virtually no blacks or persons of Eastern origin are heterozygous for AAT alleles. Some heterozygous phenotypes are statistically overrepresented in hospitalized populations and among workers with impaired lung function, suggesting that they are statistically at slightly greater risk for developing lung disease than are homozygous normal individuals. These data suggest that a screen for AAT carriers would be marginally acceptable scientifically, but would pose ethical questions of discrimination and equity in use of disease-detecting resources. Review of ethical criteria for screening, particularly the availability of experimental therapies, increases the cogency and reinforces the acceptability of performing occupational tests for both homozygous and heterozygous AAT-deficient persons. Currently, programs directed at early detection of symptomatic workers coupled with reduction or elimination of offending agents are scientifically and ethically more warranted than full-scale genetic screening for AAT deficiency.

Disease Susceptibility↗
PubMed1990

Genetic screening with exfoliated cervicovaginal cells collected by a noninvasive lavage technique performed during routine gynecologic cancer screening.

We have investigated and established the feasibility of the use of exfoliated cervicovaginal cells as an abundant source of genetic material. We routinely use this material for the detection by molecular hybridization of human papillomavirus infection of the cervix. We have analyzed deoxyribonucleic acid isolated from cervicovaginal cells by Southern blot hybridization to detect a common restriction fragment length polymorphism on chromosome 13. We suggest that in the near future most, if not all, major human genetic disease loci will be cloned and their mutations will be identified. With this knowledge and innovative methods, such as the polymerase chain reaction, it will be possible to distinguish normal individuals who harbor a variety of recessive genetic mutations that may place them at risk to produce offspring with serious genetic diseases. We propose that both genetic and cancer screening can be performed during the same office visit. Such testing offers the advantage of identification of women at risk for genetic disease with a noninvasive procedure before or concurrent with childbearing. Easily accessible genetic material extracted from exfoliated cervicovaginal cells can also be used for population genetic studies.

Adult↗
PubMed1998

Genetic screening.

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Ethics, Medical↗