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PubMed1995

The frequency of genetic eye diseases in a genetic counseling center.

The frequency of genetic eye diseases in a genetic counseling center: In this study the incidence of eye diseases of genetic origin in patients attending our genetic counseling center for a period of almost six years is documented. The frequency of retinitis pigmentosa, congenital cataracts, lens dislocation, microphthalmos, retinoblastoma, congenital glaucoma, congenital ptosis, degenerative myopia, strabismus, optic atrophy, various genetic metabolic diseases have been investigated, and the results are presented. Preventive approaches and prenatal diagnostic possibilities are discussed and the importance of genetic counseling is emphasized.

Adolescent↗
PubMed1997

An evaluation of the application of the genetic algorithm to the problem of ordering genetic loci on human chromosomes using radiation hybrid data.

We consider the problem of ordering detectable genetic loci along a chromosome by minimizing the number of obligatory breaks that can be inferred from radiation hybrid data. The problem bears some resemblance to the travelling-salesman problem, for which genetic algorithms have been used with considerable success. We find that the results from other studies on closely related problems are not directly transferable, and although we did find a genetic algorithm that performed well in this application it would appear that this algorithm is highly sensitive to any changes in the problem. Moreover, a very simple stochastic algorithm performed almost as well as our much more complicated and computer-intensive genetic algorithm and it did so in a fraction of the time. While we do not dispute that genetic algorithms can work on large complicated problems, the various modifications and fine-tuning necessary for good performance tend to be highly problem specific and they are often only arrived at after an exhaustive exploration of possibilities. Thus, we would dispute any claim that genetic algorithms are robust in their form and range of applicability.

Algorithms↗
PubMedDate not supplied

Uptake of hereditary breast/ovarian cancer genetic testing in a French national sample of BRCA1 families. The French Cancer Genetic Network.

Due to the technical difficulties involved in identifying BRCA1/2 genetic mutations, the affected patients have to be investigated before testing can be made available to all the relatives at risk. Here, we studied the attendance rates at cancer genetic clinics (CGC) and the uptake of genetic testing in first/second degree relatives after the first BRCA1 mutated woman with cancer had been informed in the family. We carried out a survey on French cancer geneticists involved in breast/ovarian CGC, asking them to select their first three BRCA1 family records. Data collection was carried out retrospectively by telephone interview with a standardised closed item questionnaire. Considering only those families (n = 37) where the index case had been informed for at least 8 months at the time of the survey, the overall attendance at CGC of first/second degree relatives (n = 419) was 31.7% (n = 133) and the overall uptake of BRCA1 testing was 26.7% (n = 112). Among those who attended the CGC (n = 133), 84.2% (n = 112) requested genetic testing (95% confidence interval: 78-90.4%). Among the first degree relatives, the unaffected women who attended accounted for 59.8% and 51.2% requested testing after the index case had been informed. Women with cancer had a higher attendance rate (83.3%) than unaffected women (36.1%) (Odds Ratio (OR) = 8.86; p < 0.001) and first degree relatives (51.4%) than second degree relatives (17.9%) (OR = 2.87; p < 0.001); women (43%) also attended more frequently than men (16%) (OR = 3.97, p < 0.001). In French BRCA1 mutated families, female first degree relatives of the index patient show the most interest in genetic testing.

Adult↗
PubMed1980

GENFILES: a computerized medical genetics information network. II. MEDGEN: the clinical genetics system.

MEDGEN, a clinical genetics information storage and retrieval system, facilitates the handling of medical records for the central genetics clinic and satellite clinics conducted by the University of California, San Francisco. The system is part of the GENFILES genetics network, which handles all of the genetics data generated by a comprehensive medical genetics center. The clinical data stored on each patient include 1) diagnoses, which utilize McKusick catalog numbers as well as our own diagnostic codes; 2) relevant medical, gestational, and pregnancy history; 3) clinical manifestations (functional and structural); 4) karyotype information through a crosslink to the cytogenetics file; 5) ethnic origin of the patients; 6) physical status and sex of the patient; 7) laboratory studies, including results of metabolic tests; and 8) any additional remarks deemed necessary for complete understanding. The data, staff member attending, and physical location of each visit also are recorded.

Computers↗
PubMed2005

Estimation of the frequency of occult mutations for an autosomal recessive disease in the presence of genetic heterogeneity: application to genetic hearing loss disorders.

The routine testing for pathologic mutation(s) in a patient's DNA has become the foundation of modern molecular genetic diagnosis. It is especially valuable when the phenotype shows genetic heterogeneity, and its importance will grow as treatments become genotype specific. However, the technology of mutation detection is imperfect and mutations are often missed. This can be especially troublesome when dealing with a recessive disorder where the combination of genetic heterogeneity and missed mutation creates an imprecision in the genotypic assessment of individuals who do not appear to have the expected complement of two pathologic mutations. This article describes a statistical approach to the estimation of the likelihood of a genetic diagnosis under these conditions. In addition to providing a means of testing for missed mutations, it also provides a method of estimating and testing for the presence of genetic heterogeneity in the absence of linkage data. Gene frequencies as well as estimates of sensitivity and specificity can be obtained as well. The test is applied to GJB2 recessive nonsyndromic deafness, Usher syndrome types Ib and IIa, and Pendred-enlarged vestibular aqueduct syndrome.

Connexin 26↗
PubMed1981

Genetic counseling and genetic services in obstetrics and gynecology: implications for educational goals and clinical practice.

Analysis of genetic counseling and antenatal diagnostic services offered by a genetics unit in a women's hospital was undertaken to identify genetic needs of the obstetrician-gynecologist. For similar reasons we tabulated findings derived from a genetic questionnaire administered routinely to obstetric registrants. Certain well-defined indications for genetic referral were identified, allowing specific educational objectives to be formulated. Potential chromosomal abnormalities constitute the most common indications for referral, particularly advance maternal age and repetitive abortions. A wide range of mendelian and polygenic/multifactorial disorders was encountered, albeit many individually rare. This suggests that the obstetrician-gynecologist should become familiar with principles of these modes of inheritance. However, educational objectives need not stress specific details of rare disorders but rather should emphasize the relatively few disorders that the obstetrician-gynecologist is likely to encounter. Realistic suggestions are offered to achieve these objectives.

Female↗
PubMed2004

Genetic red flags: clues to thinking genetically in primary care practice.

This article presents an approach to "thinking genetically" in primary care. Busy practitioners often lack the time to consider thoroughly whether their patients have an underlying genetic diagnosis. To assist the primary care clinician, a working group of the Genetics in Primary Care Faculty Development Initiative developed a simple mnemonic, Family GENES, that alerts the clinician to consider genetic causes in the differential diagnosis. In addition to family history, the red flags include Groups of anomalies, Early or Extreme presentations of common diseases, Neurodevelopmental or Neurodegenerative conditions, Exceptional or unusual pathology, and Surprising laboratory values. This article discusses the components of the mnemonic, provides examples, and gives guidelines to appropriate actions once the possibility of a genetic diagnosis has been raised.

Congenital Abnormalities↗
PubMed2005

Genetic professionals' reports of nondisclosure of genetic risk information within families.

Patients attending genetic clinics are often the main gatekeepers of information for other family members. There has been much debate about the circumstances under which professionals may have an obligation, or may be permitted, to pass on personal genetic information about their clients but without their consent to other family members. We report findings from the first prospective study investigating the frequency with which genetics professionals become concerned about the failure of clients to pass on such information to their relatives. In all, 12 UK and two Australian regional genetic services reported such cases over 12 months, including details of actions taken by professionals in response to the clients' failure to disclose information. A total of 65 cases of non-disclosure were reported, representing <1% of the genetic clinic consultations in the collaborating centres during the study period. These included 39 cases of the failure of parents not passing full information to their adult offspring, 22 cases where siblings or other relatives were not given information and four cases where information was withheld from partners -- including former and prospective partners. Professionals reported clients' reasons for withholding information as complex, more often citing concern and the desire to shield relatives from distress rather than poor family relationships. In most cases, the professionals took further steps to persuade their clients to make a disclosure but in no instance did the professional force a disclosure without the client's consent.

Attitude of Health Personnel↗
PubMed2004

Population genetic structure of and inbreeding in an insular cattle breed, the Jersey, and its implications for genetic resource management.

The Jersey is a ubiquitous and successful breed of cattle that originates from the UK Channel Island of Jersey. While the breed has been exported extensively, no imports have taken place to the island since 1789, leading to a concern regarding possible losses of genetic diversity and increased inbreeding. We have conducted the first large-scale genetic analysis of the Jersey cattle using only samples from the island. A total of 223 cattle from all parishes except one were genotyped for 12 microsatellite loci. The average number of alleles per locus and expected heterozygosity were found to be comparatively high (n(A)=4, H(e)=0.64) with respect to that observed in a number of continental breeds. Only breeds that have been upgraded and are therefore the result of admixture are clearly more variable than the Jersey. We also found a significant but limited amount of genetic differentiation between parishes (F(st)=0.013), or even between farms (F(st)=0.035) despite an apparent lack of movement. This is confirmed by the application of two recent statistical methods. A Bayesian partition analysis shows that the most probable value of K, the number of possible hidden partitions, is 1 (P approximately 0.98). K=2 has a much lower probability (P approximately 0.02) while other values are essentially zero. Similarly, we were able to show that there was no support for departure from panmixia other than due to population structure, and thus that there is sufficient background gene flow across the island to overcome local drift. Overall, it appears that the current level of genetic diversity and its distribution within the island means it is unnecessary to import unrelated genetic material to the island for management purposes.

Alleles↗
PubMed1998

The use of genetic tests and genetic information by life insurance companies: does this differ from the use of routine medical information?

Questions regarding insurance companies' access to and use of genetic test results and genetic information have been raised since the advent of the Human Genome Project. The ability to place applicants of similar risks in groups, a process known as underwriting, is critical to the availability and affordability of individually underwritten life, disability income, and long-term care insurance. This paper focuses on how life insurance companies use medical information and particularly genetic test results and other genetic information in the risk assessment process. Issues and concerns raised about differences between routine medical information and genetic information are addressed and policies with regard to privacy and confidentiality are presented.

Confidentiality↗
PubMed2000

Allele-specific PCR shows that genetic exchange occurs among genetically diverse Nodularia (cyanobacteria) filaments in the Baltic Sea.

Some cyanobacteria have been shown to exchange genetic information under laboratory conditions, but it has not been clear whether such genetic exchange occurs in the natural environment. To address this, a population genetic study was carried out on the filamentous diazotrophic cyanobacterium Nodularia in the Baltic Sea. Nodularia filaments were collected from 20 widely distributed sampling stations in the Baltic Sea during June and July 1998. Allele-specific PCR (AS-PCR) was used to characterize over 2000 filaments at three loci: a non-coding spacer between adjacent copies of the main structural gas vesicle gene gvpA (gvpA-IGS), the phycocyanin intergenic spacer (PC-IGS) and the rDNA internal transcribed spacer (rDNA-ITS). The three loci were all found to be polymorphic in the 1998 population: two alternative alleles were distinguished at the gvpA-IGS and PC-IGS loci, and three at the rDNA-ITS locus. All 12 possible combinations of alleles were found in the filaments studied, but some were much more common than others. The index of association (I:(A)) for all possible pairwise combinations of isolates was found to differ significantly from zero, which implies that there is some linkage disequilibrium between loci. The I:(A) values for 16 out of 20 individual sampling stations also differed significantly from zero: this shows that the observed linkage disequilibrium is not due to pooling data from genetically distinct subpopulations. Monte-Carlo simulations with random subsets of the data confirmed that some combinations showed significantly more linkage disequilibrium than expected by chance alone. It is concluded that genetic exchange occurs in the natural Nodularia population, but the frequency is not high enough for the loci to be in linkage equilibrium. The distribution of the 12 genotypes across the Baltic Sea was found to be non-random, but did not correlate with temperature, salinity or major nutrient concentrations. A significant relationship was found between the gene diversity among filaments at each station and the distance of the station from the centre of the sampling area: possible reasons for this trend are discussed.

Alleles↗
PubMed1997

Genetic linkage study of familial Mediterranean fever (FMF) to 16p13.3 and evidence for genetic heterogeneity in the Turkish population.

Familial Mediterranean fever (FMF) is an autosomal recessive condition that is almost entirely restricted to the non-Askhenazi Jews, Arabs, Armenians, and Turks. Genetic linkage study of a large group of non-Turkish families has previously mapped the FMF locus to the 16p13.3 region and shown that this locus resides 0.305 cM distal to D16S246. Furthermore, allelic association has also been shown with D16S3070 (75%) and D16S3275 (66%). However, no genetic heterogeneity has been described for any of the three major reported groups of FMF families. Here, we describe the genetic linkage relationship of the fourth major group of Turkish families and report the first evidence for genetic heterogeneity of this condition. Two point linkage analysis and haplotype inspection of 15 DNA markers from the reported region of the FMF locus identified tight linkage in a group of six Turkish FMF families. A maximum lod score of 9.115 at theta = 0.00 was observed for D16S3024. Nine other DNA markers provided similar evidence of linkage with lod score values of above 5.21. However, two other FMF families were completely unlinked to this region of chromosome 16. Haplotype construction of DNA markers in five consanguineous linked families showed that a segment of homozygosity has been conserved for D16S3070 and D16S2617. No other DNA markers showed any such conservation. Therefore, we suggested that these two markers reside in close proximity to the FMF locus. Furthermore, we observed 80% allelic association with D16S2617 but no association with D16S3070 or any other DNA markers from the FMF critical region. In summary, we conclude that our Turkish families are also linked to the reported FMF locus at 16p13.3, there is a genetic heterogeneity for this condition at least in our group of Turkish families, and D16S2617 is in linkage disequilibrium in the Turkish FMF families. Combination of this study with previously published observations suggests that the FMF locus resides between D16S246 and D16S3070/D16S2617 and within a region of about 250-300 kb.

Adolescent↗
PubMed2002

Genetic testing and genetic counselling in hypertrophic cardiomyopathy: the French experience.

AIMS: A major breakthrough in the molecular genetics of hypertrophic cardiomyopathy (HCM) has made genetic testing now available in clinical practice, raising new questions about its implications, potential benefits, and the organisation of the procedure. The aim of this work was (1) to discuss the different questions related to genetic testing in HCM, and propose guidelines for the different situations, (2) to report our preliminary experience with a specific procedure. METHODS AND RESULTS: The main questions asked by patients and relatives concern presymptomatic diagnosis and prenatal counselling/diagnosis, while clinicians sometimes discuss diagnostic and prognostic testing. To take into account the complex medical and psychological implications of this new approach, we developed a specific, multidisciplinary, and multiple step procedure, including a cardiologist, a geneticist, and a psychologist. Seventy subjects were examined, including (1) 29 adults for presymptomatic diagnosis (of whom 10 left the procedure after the first visit and 19 continued, among whom six had a mutation and two experienced negative psychological impact, observed during follow up), (2) nine couples of parents for presymptomatic diagnosis in their children (the procedure was stopped after the first visit in eight and continued in one), (3) 22 couples for prenatal counselling (no prenatal genetic testing was asked for after the first visit), and (4) 10 subjects for diagnostic testing. We decided to perform no prognostic testing. CONCLUSION: Our preliminary experience confirms the complexity of the situation and suggests the necessity for a specific procedure to ensure good practice in genetic testing of HCM.

Adolescent↗
PubMed2004

The National Pork Producers Council Maternal Line National Genetic Evaluation Program: a comparison of six maternal genetic lines for female productivity measures over four parities.

Litter (n = 8,424) and female performance records were collected in two breed-to-wean production units in order to evaluate genetic line differences for sow longevity and maternal performance over four parities. Lines evaluated were American Diamond Genetics, Danbred North America, Dekalb-Monsanto DK44, Dekalb-Monsanto GPK347, Newsham Hybrids, and National Swine Registry. Females within a line were derived from a minimum of 65 sires, 197 dams (three dams per sire), and a maximum of three daughters per dam, except in the GPK347, which were produced using semen from 12 Nebraska Index boars mated with Dekalb-Monsanto Line 34 females. All lines expressed 100% maternal heterosis. Mixed model statistical procedures were used with fixed effects including genetic line, parity, production unit, and two-way interactions. Random effects included a contemporary week of production and female for repeated records. Lactation length (average 15 d) was included as a linear covariate where appropriate. In total, 3,599 females entered as early-weaned pigs, 3,283 entered the breeding herd, 2,592 farrowed at least a single litter, and 1,656 and completed four parities. Line (P < 0.001) and parity (P < 0.001) effects were observed for virtually all traits measured. Ranges of genetic line differences averaged across parities were 1.76 pigs for total born, 1.45 pigs born alive, and 0.31 stillborn pigs per litter. Ranges of line differences in total and live litter weight were 1.4 and 1.3 kg, respectively. Ranges among lines, within Parities 1 through 4, for litter size at weaning were 0.56, 1.08, 0.91, and 0.64 pigs per litter, respectively. Line differences for weight (33.8 kg) and backfat depth (6.4 mm) at farrowing, lactation feed intake (8.7 kg), weight loss (5.0 kg), and backfat loss (0.87 mm) were observed. Extended wean-to-estrus interval was related to variation in weight, feed intake, and backfat loss in all lines except the GPK347. The GPK347 females farrowed and weaned the largest number of pigs, ate less feed in lactation, and lost more backfat and weight during lactation, yet they had the largest litters and the shortest wean-to-estrus intervals. Line x parity interactions existed for many traits due to small rank changes, but in general, the high- and low-ranked lines did not change. Genetic line differences in reproductive efficiency through four parities exist and must be recognized when choosing a female line.

Adipose Tissue↗
PubMed1997

Genetic polymorphisms in human drug-metabolizing enzymes: potential uses of reverse genetics to identify genes of toxicological relevance.

The human mind was engaged with fundamental questions on the nature of heredity long before the study of genetics became a scientific discipline. Many traits, such as height, eye color, blood pressure, or cancer susceptibility, have been known to run in families, although the genes or combination of genes that underlie these observable characteristics remain unknown in most cases. Differences in susceptibility to environmental agents in humans are likewise determined by variations in genetic background--genetic polymorphisms. In this article, we review the current status of studies on human polymorphisms in drug-metabolizing enzymes and discuss various approaches to the analysis of genetic polymorphisms. We expect that in the near future, novel methods in genetic analysis of human populations will be likely to play a key role in the identification of genes of toxicological relevance.

Cytochrome P-450 Enzyme System↗
PubMed1999

Genetics and child psychiatry: I Advances in quantitative and molecular genetics.

Advances in quantitative psychiatric genetics as a whole are reviewed with respect to conceptual and methodological issues in relation to statistical model fitting, new genetic designs, twin and adoptee studies, definition of the phenotype, pervasiveness of genetic influences, pervasiveness of environmental influences, shared and nonshared environmental effects, and nature-nurture interplay. Advances in molecular genetics are discussed in relation to the shifts in research strategies to investigate multifactorial disorders (affected relative linkage designs, association strategies, and quantitative trait loci studies); new techniques and identified genetic mechanisms (expansion of trinucleotide repeats, genomic imprinting, mitochondrial DNA, fluorescent in-situ hybridisation, behavioural phenotypes, and animal models); and the successful localisation of genes.

Adolescent↗
PubMedDate not supplied

Genetic secrets: social issues of medical screening in a genetic age.

In the 1990s, as the multi-billion-dollar Human Genome Project makes more and more genetic information available, we would do well to look closely at the social context of power dynamics, control, and economic interests within which that information will be used. Let us consider four specific questions. How does social stratification by race, ethnicity, gender, and social class affect the use of genetic information in the workplace? In what ways are perspectives on genetic testing socially located? What can fetal exclusion policies teach us about how genetic information might be used to identify high-risk individuals? What social and political challenges are posed by new information about genetic abnormalities, and how might that information be distributed fairly?

Administrative Personnel↗
PubMedDate not supplied

[The genetic differentiation of mammalian taxa: their assessment by biochemical genetic markers].

A review of data on genetic differentiation of mammalian taxa has been made on the basis of estimating the percent of fixed gene differences (PFD). The results substantiate the existence of evident differences in the scale of genetic divergence between taxa in different mammalian orders. Among smaller mammals (marsupials, insectivores, chiropterans, myomorph and sciuromorph rodents, african mole rats, and elephant shrews) interspecific differences within a genus involve the average of 25-40% of investigated loci. At the genetic level the value is 50-60%, whereas at the familial level the differences are beyond the resolution capacity of the method (PFD = 60-80%). Orders of larger mammals can be divided into two subgroups. One of them that includes carnivores, artiodactylans, and hystricomorph rodents is characterised by PFD values of 10-14%, 30-50%, and 69-70% at respective levels. The other subgroup composed of proboscideans, primates, pinnipeds, and toothed whales, has a low level of genetic divergence expressed by PFD values of 0-3%, 7-36%, and 50-60% at species, generic and familial levels, respectively. Insufficiency of data on baleen whales and perissodactyls does not allow to cluster them ultimately with any of these groups. There are three possible, but not necessarily alternative, causes for the observed differences in genetic divergence: 1) over-ranking of genera in larger mammals; 2) different paleontological age of orders; 3) unequal rates of molecular evolution.

Animals↗