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PubMed2002

No accident: genetic codes freeze in error-correcting patterns of the standard genetic code.

The standard genetic code poses a challenge in understanding the evolution of information processing at a fundamental level of biological organization. Genetic codes are generally coadapted with, or 'frozen' by, the protein-coding genes that they translate, and so cannot easily change by natural selection. Yet the standard code has a significantly non-random pattern that corrects common errors in the transmission of information in protein-coding genes. Because of the freezing effect and for other reasons, this pattern has been proposed not to be due to selection but rather to be incidental to other evolutionary forces or even entirely accidental. We present results from a deterministic population genetic model of code-message coevolution. We explicitly represent the freezing effect of genes on genetic codes and the perturbative effect of changes in genetic codes on genes. We incorporate characteristic patterns of mutation and translational error, namely, transition bias and positional asymmetry, respectively. Repeated selection over small successive changes produces genetic codes that are substantially, but not optimally, error correcting. In particular, our model reproduces the error-correcting patterns of the standard genetic code. Aspects of our model and results may be applicable to the general problem of adaptation to error in other natural information-processing systems.

Animals↗

PubMed2006

Genetic knowledge and moral responsibility: ambiguity at the interface of genetic research and clinical practice.

Despite a rapidly expanding literature on the issue of duty to warn at-risk relatives in the context of clinical genetic testing, little has been written on parallel issues with regard to the management of genetic research results. Some might view this lack as an indication that there is little to discuss in this regard. That is, standard practice is that data obtained through medical research should not be treated as though they are clinically relevant, and this standard should hold for genetic research as well. This paper challenges this conclusion and its underlying assumptions. We argue that the line between genetic research and clinical practice is often ambiguous. In some cases, research data gathered from a very small number of subjects could have immediate clinical implications. Hence, it is unethical for genetic researchers to absolve themselves of clinical responsibilities for research subjects and/or their families, on the grounds that the data were obtained for research purposes. Indeed, we argue that it could well be unethical to embark on some forms of genetic research unless advance arrangements have been made for genetic counseling and clinical follow-up. Furthermore, in some cases, it might be unethical to enroll subjects in studies if the subjects are unwilling to receive their individual results.

Arrhythmogenic Right Ventricular Dysplasia↗

PubMed2005

Community genetics: a bridge between clinical genetics and public health.

Clinical genetics and public health differ in their subjects; in who takes the initiative; in their aims, methods and outcome measures, and therefore in their ability to handle sensitive issues. They are seemingly incompatible. Nevertheless, they can be reconciled in community genetics. Community genetics combines the best from clinical genetics and public health. It shares with clinical genetics its aim of empowerment, its methods of information and support, its outcome measures and its possibility to handle sensitive issues. It has in common with public health its subjects; the origin of its initiatives, and non-reproductive prevention. In general, communities can be defined at different levels: geographically, linguistically, socially or genetically. Genetic communities can also be defined at different levels: on the basis of common heritage, on the basis of common practice, or on the basis of common problems.

Genetic Predisposition to Disease↗

PubMed2000

Premarital genetic investigations: effect of genetic counselling.

Over a period of 2 years, 86 couples (172 cases) were referred to the genetics clinic of the National Research Centre for premarital genetic counselling. About 73.25% had a family history of different genetic disorders. Consanguinity was found in 86.04%. Genetic investigations revealed chromosomal abnormalities in 26 cases (15.11%); 23 cases (13.37%) had other abnormal results. After genetic counselling, postconceptional follow-up was carried out for 30 couples; 10 of them required amniocentesis that showed abnormal fetuses in 2 mothers. Other couples had normal offspring. We conclude that premarital genetic counselling is of great use in the detection of genetic disorders and is an essential step in changing attitudes towards premarital testing and reducing consanguineous marriage.

Adolescent↗

PubMed2003

[Genetics and respiratory control: studies in normal humans and genetically modified animals].

INTRODUCTION: Studies into the contribution of genetic factors to respiratory control disorders are scarce, with impediments to their conduct including difficulties in characterizing these disorders, the large number of genes involved in respiratory control, and interactions between genetic and environmental factors. STATE OF THE ART: The rare congenital central hypoventilation syndrome (CCHS) has opened up the field of respiratory control genetics. Heterozygous mutations of genes involved in neural crest development were discovered recently. Studies in mutant mice have identified respiratory control disturbances related to loss of function of genes involved in neural crest development, genes encoding transcription factors, diffusible factors, and proteins contributing to neurotransmission. PERSPECTIVES: Future genetic epidemiological studies in humans and new models of mutant mice should describe genes involved in respiratory control. Better knowledge of CCHS genetics should provide guideposts for investigating the genetics of other respiratory control disorders. CONCLUSIONS: Respiratory control genetics is opening up new paths for research into respiratory physiology and pathophysiology.

Adolescent↗

PubMed2003

Genetic testing and its implications: human genetics researchers grapple with ethical issues.

To better understand ethical issues involved in the field of human genetics and promote debate within the scientific community, the author surveyed scientists who engage in human genetics research about the pros, cons, and ethical implications of genetic testing. This study contributes systematic data on attitudes of scientific experts. The survey finds respondents are highly supportive of voluntary testing and the right to know one's genetic heritage. The majority consider in utero testing and consequent pregnancy termination acceptable for cases involving likelihood of serious disease but disapprove for genetic reasons they consider arbitrary, leaving a gray area of distinguishing between treatment of disorders and enhancement still to be resolved. While safeguarding patient confidentiality versus protecting at-risk third parties (kin, reproductive partners) presents a dilemma, preserving privacy from misuse by institutional third parties (employers, insurers) garners strong consensus for legislation against discrimination. Finally, a call is made for greater genetic literacy.

Abortion, Eugenic↗

PubMed2003

A clinical-genetic study of Parkinson's disease in a genetically isolated community.

The role of genetic factors in idiopathic, late-onset Parkinson's disease (PD) remains unclear, in spite of the recent advances in the genetics of early-onset forms of familial parkinsonism. There is increasing interest in using genetically isolated populations to unravel the genetics of complex diseases such as late-onset PD. We have studied genetic and clinical features of 109 patients with parkinsonism from an area comprising a genetically isolated population in the South-West of the Netherlands. Of the 109 patients with ascertained parkinsonism, 41 patients were diagnosed with PD and could be linked to a common founder 14 generations ago. The distribution of ages at onset of PD in the genetically isolated population was significantly bimodal, showing two peaks (one with a mean at age 67 years and another with a mean at 44 years, the former peak being significantly larger than that in a population-based study, the Rotterdam Study). In other clinical features, the only statistically significant difference between early-onset and late-onset PD was a decreased motor and cognitive function in patients with late-onset PD. Involvement of other PD genes including DJ-1, a gene implicated in a kindred with early-onset parkinsonism from the same genetic isolate, was excluded in other PD patients in the population. The finding of a common ancestor in 41 idiopathic-PD patients along with the exclusion of known PD genes and loci suggests the presence of at least one other, yet unknown, susceptibility gene involved in PD in this population.

Adult↗

PubMed2001

Multiple genetic alterations involved in the tumorigenesis of human cholangiocarcinoma: a molecular genetic and clinicopathological study.

PURPOSE: Cholangiocarcinoma (CC) is the second most common malignant tumor in the liver and the molecular genetic alterations involved in the tumorigenesis of CC have not been well studied. PATIENTS AND METHODS: The authors analyzed the loss of heterozygosity (LOH) in four tumor suppressor genes, including the adenomatous polyposis coli (APC) gene, the deleted in colon cancer (DCC) gene, the 8-hydroguanine-specific DNA glycosylase (OGG1) gene, and the p53 gene in 22 surgically resected primary CCs by using microdissection-based PCR amplification and direct DNA sequencing. RESULTS: A total of 19 (86.4%) out of 22 CCs exhibited genetic alterations, of which 11 (57.9%) and eight (42.1%) cases showed one and more than one gene alterations, respectively. The frequency of genetic alterations of the four genes studied ranged in order from high to low as APC (68.8%) > DCC (46.2%) > OGG1 (41.7%) > p53 (37.5%). Based on the pattern of altered genes and their correlation with clinical and pathological parameters, the genetic alterations were classified into three groups: group I: no detectable genetic alterations (n = 3, 13.6%); group II: LOH in APC and/or DCC (n = 9, 40.9%); and group III: LOH in OGG1 and/or p53 occurred separately or combined with LOH in APC and/or DCC (n = 10, 45.5%). The > or = 3-year survival rates between group II and group III are 88.9% and 30%, respectively (P < 0.05). No significant differences were found between genetic alterations and tumor size, tumor type, tumor invasion, TNM staging, and tumor differentiation (P > 0.05). CONCLUSION: Accumulation of multiple genetic alterations are involved in the tumorigenesis of CC, of which genetic alterations of APC and DCC occur at a relatively early stage, and of OGG1 and p53 occur at a relatively late stage during development of CC.

Aged↗

PubMed2003

[MapDraw: a microsoft excel macro for drawing genetic linkage maps based on given genetic linkage data].

MAPMAKER is one of the most widely used computer software package for constructing genetic linkage maps.However, the PC version, MAPMAKER 3.0 for PC, could not draw the genetic linkage maps that its Macintosh version, MAPMAKER 3.0 for Macintosh,was able to do. Especially in recent years, Macintosh computer is much less popular than PC. Most of the geneticists use PC to analyze their genetic linkage data. So a new computer software to draw the same genetic linkage maps on PC as the MAPMAKER for Macintosh to do on Macintosh has been crying for. Microsoft Excel,one component of Microsoft Office package, is one of the most popular software in laboratory data processing. Microsoft Visual Basic for Applications (VBA) is one of the most powerful functions of Microsoft Excel. Using this program language, we can take creative control of Excel, including genetic linkage map construction, automatic data processing and more. In this paper, a Microsoft Excel macro called MapDraw is constructed to draw genetic linkage maps on PC computer based on given genetic linkage data. Use this software,you can freely construct beautiful genetic linkage map in Excel and freely edit and copy it to Word or other application. This software is just an Excel format file. You can freely copy it from ftp://211.69.140.177 or ftp://brassica.hzau.edu.cn and the source code can be found in Excel's Visual Basic Editor.

English Abstract↗

PubMed2003

"Genetic exceptionalism" in medicine: clarifying the differences between genetic and nongenetic tests.

Predictive genetic tests are now available for assessing susceptibility to a variety of conditions, including breast and colon cancer, hemochromatosis, and Alzheimer and Huntington disease. Much controversy surrounds the application of these tests, stemming from their similarities to and differences from other tests commonly used in asymptomatic persons. Some have argued that genetic tests are unique and therefore justify special consideration with regard to informed consent and privacy. This paper examines the arguments for such "genetic exceptionalism" and concludes that no clear, significant distinctions between genetic and nongenetic tests justify a different approach to testing by clinicians. Nevertheless, with many genetic tests, the results may cause stigmatization, family discord, and psychological distress. Regardless of whether a test is genetic, when this combination of characteristics is present and when health care providers are not specifically trained to interpret results, testing should be performed with particular caution and the highest standards of informed consent and privacy protection should be applied.

Ethics, Medical↗

PubMed1999

Promoting safe and effective genetic tests in the United States: work of the task force on genetic testing.

The Task Force on Genetic Testing was created to review genetic testing in the United States and, when necessary, to make recommendations to ensure the development of safe and effective genetic tests. A survey to explore the state of genetic testing was undertaken for the Task Force and completed in early 1995. The survey, as well as literature reports and other information collected for the Task Force, showed problems affecting safety and effectiveness, as defined by the Task Force: validity and utility of predictive tests, laboratory quality, and appropriate use by healthcare providers and consumers. On the basis of these findings, the Task Force made several recommendations to ensure safe and effective genetic testing. The Secretary of Health and Human Services followed up one recommendation by creating the Secretary's Advisory Committee on Genetic Testing. One of its functions will be to implement other recommendations of the Task Force.

Genetic Techniques↗

PubMed1999

Genetic testing, genetic medicine, and managed care.

As modern human genetics moves from the research setting to the clinical setting, it will encounter the managed care system. Issues of cost, access, and quality of care will affect the availability and nature of genetic testing, genetic counseling, and genetic therapies. This Article will explore such issues as professional education, coverage of genetic services, privacy and confidentiality, and liability. It will conclude with a series of recommendations for the practice of genetic medicine in the age of managed care.

Confidentiality↗

PubMed2000

Goals, benefits, and outcomes of genetic counseling: client and genetic counselor assessment.

Most studies of outcomes of genetic counseling have focused on client knowledge, reproductive plans and behavior, or satisfaction. Other measures of the "value" of genetic counseling are needed to guide research assessing the impact of genetic counseling on individuals and populations, as well as to improve the process of providing care. To obtain input from providers, we conducted telephone interviews with six experienced genetic counselors, and then we held a focus group with 10 additional genetic counselors from a variety of practice settings. To obtain input from consumers, telephone interviews were also conducted with 19 past clients of these participating counselors. We found that counselor goals focus on meeting clients' needs, usually educating and providing psychosocial support. Clients often had few goals going into a session because they were unaware of what would be discussed or how the session would be structured. They usually did not expect to receive "counseling," and when they did, it was a welcome surprise. Both clients and counselors commented that a positive interpersonal interaction and "connecting" are primary measures of success. All clients appreciated the large amount of time spent with the counselor, and the manner (clear, comprehensive, and unhurried) of providing information. Many clients said that genetic counseling resulted in improved communication with their partners and other family members. Clients view the counselor as an "expert" and value the counselor as an on-going resource for both information and support. These "outcomes"f genetic counseling need to be assessed, and new measures must be developed.

Adult↗

PubMed2006

Attitudes of genetic counselors towards expanding newborn screening and offering predictive genetic testing to children.

There is movement to expand newborn screening (NBS) to include conditions that challenge the traditional public health screening criteria. Little is known about the attitudes of genetic counselors towards expanding NBS and offering predictive genetic tests to children. For our study genetic counselors completed an internet survey posted on the National Society of Genetic Counselors Listserv regarding five conditions: cystic fibrosis (CF), Duchenne muscular dystrophy (DMD), glucose-6-phosphate dehydrogenase deficiency (G6PD), fragile X (FraX), and type 1 diabetes (T1D). The survey addressed attitudes towards: (1) testing high-risk infants; (2) mandatory NBS; (3) population screening beyond the newborn period; and (4) testing one's own child. Two hundred sixty-seven usable surveys were received. Over two-thirds of respondents supported testing high-risk infants for all conditions except T1D (22%). CF was the only condition for which there was majority support for both mandatory NBS (56%) and later population screening (60%). For all other conditions, later population screening was preferred over NBS (P <or= 0.01). Genetic counselors were most likely to test their own child for CF (46%) and least likely to test their own child for T1D (6%). For each condition, genetic counselors were more likely to support NBS if they chose to screen their own newborn (P < 0.001). Attitudes towards NBS were not influenced by year of graduation or professional experience. We can conclude that genetic counselors are supportive of targeted testing of high-risk infants. They prefer voluntary population screening with consent to mandatory NBS for conditions that challenge Wilson and Jungner criteria. Their support for NBS correlates with their interest in testing their own children and not with professional experience.

Attitude of Health Personnel↗

PubMed2002

Worry and attitude of men in at-risk families for prostate cancer about genetic susceptibility and genetic testing.

BACKGROUND: The aim of this study was to evaluate worry about genetic susceptibility and the attitude of men with family history of prostate cancer (CaP) toward genetic testing. METHODS: Three hundred seventy-five eligible first-degree relatives (FDR) of men with CaP, were asked to participate in a screening and to fill out a survey covering the worry about genetic susceptibility and interest in genetic testing. RESULTS: Of the 375 candidates contacted, 277 completed the survey, and had undergone PSA measurement. Sixty-four percent worried a little or not at all about inherited predisposition to CaP, while the remainder worried a lot or extremely. The candidates who worried a lot or extremely were men with high levels of durable anxiety disposition (STAI trait), who had undergone a previous screening procedure and men with sons. Ninety-eight percent of men expressed their interest in undergoing genetic testing. The most motivated candidates to have the test done were men with several relatives with CaP. CONCLUSIONS: The level of worry about genetic susceptibility was low and there was a concrete interest in genetic testing in FDR of men with CaP. This interest increased with the number of CaP in the family.

Adult↗

PubMed2001

Genetic counseling and interpretation of genetic tests in familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer.

PURPOSE: Genetic counseling and interpreting genetic test results can be complex. Moreover, without knowing the limitations of the methods used and the lifetime probability of developing cancer in individuals who carry a gene that predisposes to cancer, misinterpretation may lead to false assurance. The purpose of this review is to discuss how genetic counseling will benefit patients and their family, the genetic tests available for hereditary colorectal cancer syndromes, and the interpretation of results. METHODS: Current literature was reviewed and our clinical and research experiences were incorporated. RESULTS: This review serves as a guide to enable various health care providers to better counsel patients in their quest for advice on prevention, early detection, and surveillance for colorectal cancer. Notable topics of discussion are who should undergo genetic counseling and consider testing and how the interpretation of test results can be misleading; for example, understanding the difference between a no mutation detected vs. a negative test result. CONCLUSIONS: Genetic counseling is of paramount importance for patients to fully understand the limitations of genetic testing and will aid in the management of patients who are susceptible to colorectal cancer.

Adenomatous Polyposis Coli↗

PubMed2003

Microsatellite analysis of genetic diversity and population genetic structure of a wild rice (Oryza rufipogon Griff.) in China.

Genetic diversity and population genetic structure of natural Oryza rufipogon populations in China were studied based on ten microsatellite loci. For a total of 237 individuals of 12 populations collected from four regions, a moderate to high level of genetic diversity was observed at population levels with the number of alleles per locus ( A) ranging from 2 to 18 (average 10.6), and polymorphic loci ( P) from 40.0% to 100% (average 83.3%). The observed heterozygosity ( H(O)) varied from 0.163 to 0.550 with the mean of 0.332, and the expected heterozygosity ( H(E)) from 0.164 to 0.648 with the mean of 0.413. The level of genetic diversity for Guangxi was the highest. These results are in good agreement with previous allozyme and RAPD studies. However, it was unexpected that high genetic differentiation among populations was found ( R(ST) = 0.5199, theta = 0.491), suggesting that about one-half of the genetic variation existed between the populations. Differentiation (pairwise theta) was positively correlated with geographical distance ( r = 0.464), as expected under the isolation by distance model. The habitat destruction and degradation throughout the geographic range of O. rufipogon may be the main factor attributed to high genetic differentiation among populations of O. rufipogon in China.

China↗

PubMed2003

Genetic diversity of oil palm (Elaeis guineensis Jacq.) germplasm collections from Africa: implications for improvement and conservation of genetic resources.

A total of 723 accessions of oil palm ( Elaeis guineensis Jacq.) from 26 populations representing ten countries in Africa and one Deli dura family were screened for allelic variation at seven enzyme loci from six enzyme systems using starch gel electrophoresis. On average, 54.5% of the loci were polymorphic (0.99 criterion). The average and effective number of alleles per locus was 1.80 and 1.35, respectively. Mean expected heterozygosity was 0.184, with values ranging from 0.109 (population 8, Senegal) to 0.261 (population 29, Cameroon). The genetic differentiation among populations was high (F(ST)=0.301), indicating high genetic divergence. The calculation of F(ST) by geographic zones revealed that the high F(ST) was largely due to F(ST) among populations in West Africa, suggesting diversifying selection in this region. The mean genetic distance across populations was 0.113. The lowest genetic distance (D) was observed between population 5 from Tanzania and population 7 from the Democratic Republic of the Congo (0.000) and the highest was found between population 4 from Madagascar and population 13 from Sierra Leone (0.568). The total gene flow across oil palm populations was low, with an Nm of 0.576, enhancing genetic structuring, as evident from the high F(ST) values. UPGMA cluster analysis revealed three main clusters; the western outlying populations from Senegal and Sierra Leone were in one cluster but separated into two distinct sub-clusters; the eastern outlying populations from Madagascar were in one cluster; the populations from Angola, Cameroon, The Democratic Republic of the Congo, Ghana, Tanzania, Nigeria and Guinea were in one cluster. The Deli dura family seems to be closely related to population 6 from Guinea. Oil palm populations with high genetic diversity-i.e. all of the populations from Nigeria, Cameroon and Sierra Leone, population 6 of Guinea, population 1 of Madagascar and population 2 of Senegal should be used in improvement programmes, whereas for conservation purposes, oil palm populations with high allelic diversity (A(e)), which include populations 22 and 29 from Cameroon, populations 39 and 45 from Nigeria, population 6 from Guinea, populations 5 and 13 from Sierra Leone and population 1 from Madagascar should be selected for capturing as much genetic variation as possible.

Africa↗