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PubMed1999

Genetic characterization of the nef gene from human immunodeficiency virus type 1 group M strains representing genetic subtypes A, B, C, E, F, G, and H.

Most efforts to characterize sequence variation of HIV isolates has been directed toward the structural envelope gene. Few studies have evaluated the sequence variability of auxiliary genes such as nef. In this study 41 new HIV-1 strains, representing the majority of the described envelope subtypes of HIV-1 (A to H), were genetically characterized in the nef region. Phylogenetic analysis showed that 34 strains could be classified in the same subtype in nef and env, and 7 (19%) of the 41 new viruses were recombinants. For two of the seven strains, recombination occurred upstream of the nef gene, whereas for five of the seven strains recombination occurred within the nef gene with a crossover close to the 5' end of the LTR (long terminal repeat). The low intersubtype distance between subtype B and D in the nef gene confirms previous observations in the pol, env, and gag genes, which suggest a common ancestor for these subtypes. The majority of all the previously described functional domains in the nef gene were relatively conserved among the different subtypes, with only minor differences being observed. The myristoylation signal among the different subtypes, with only minor differences being observed. The myristoylation signal was less conserved for subtype C, with one or more amino acid changes being observed at positions 3, 4, and 5. The highly conserved acidic region (positions 62 to 65), critical for the enhancement of viral synthesis with an increased virus growth rate, was less conserved among the subtype G strains from our study. At least three epitopic regions of the nef gene have been defined and each can be recognized by CTLs under a variety of HLA restrictions; all were also relatively well conserved between the different genetic subtypes. Despite the relatively important genetic variation in nef sequences obtained among the different genetic subtypes, functional domains and CTL epitopes were relatively well conserved. In vitro and/or in vivo studies are necessary to study the relevance of the observed differences.

Amino Acid Sequence↗

PubMed1994

Genetic analysis of HIV-1 isolates from Brazil reveals presence of two distinct genetic subtypes.

The spread of the human immunodeficiency virus type 1 (HIV-1) is by now virtually worldwide. An understanding of the genetic, biological, and immunological differences among isolates collected in different geographic locales is crucial for the development of globally effective vaccines. Here we report the genetic characteristics of 21 HIV-1 isolates from Brazil. The isolates were initially characterized using a heteroduplex mobility assay. The majority (17 of 21) were related to North American/European reference isolates of genetic subtype B. Four isolates belonged to a more recently identified genotype, termed subtype F. The subtype F sequences from Brazil are distinguishable in both gag and env from five other genetic subtypes of HIV-1 currently recognized. Like many locales, Brazil harbors more than one HIV-1 subtype.

AIDS Vaccines↗

PubMed1974

Mitochondrial genetics. VI. The petite mutation in Saccharomyces cerevisiae: interrelations between the loss of the p+ factor and the loss of the drug resistance mitochondrial genetic markers.

The survival of the rho(+) factor and of Drug(R) mitochondrial genetic markers after exposure to ethidium bromide has been studied. A technique allowing the determination of Drug(R) genetic markers among a great number of both grande and petite colonies has been developed. The results have been analyzed by the target theory. The survival of the rho(+) factor is always less than the survival of any Drug(R) genetic marker. The survivals of C(R) and E(R) are similar to each other, while that of O(R) is greater than that of the other two Drug(R) markers. All possible combinations of Drug(R) markers have been found among the rho(-) petite cells induced, while the only type found among the grande colonies is the preexisting one. The loss of the C(R) and E(R) genetic markers was found to be the most frequently concomitant, while the correlation between the loss of the O(R) marker and the other two Drug(R) markers is less strong. Similar results have been obtained after U.V. irradiation. Interpretations concerning the structure of the yeast mitochondrial genome are given and hypotheses on the mechanism of petite mutation discussed.

Drug Resistance, Microbial↗

PubMed2000

Genetics of growth and reproduction in the turkey. 14. Changes in genetic parameters over thirty generations of selection for increased body weight.

A line (F) of turkeys was selected over 30 generations for increased 16-wk BW. The base population for the F line was a randombred control population (RBC2) that was maintained without conscious selection and used to remove yearly environmental variation in the F line. Selection was effective in increasing 16-wk BW in the F line. Selection differentials based on the mean of selected parents minus mean of entire population (intended) and intended selection differentials weighted for number of offspring produced (actual) did not consistently differ, indicating that natural selection was not significantly opposing artificial selection. The realized heritability (h2) of 16-wk BW in the F line, based on the linear regression of the selection response on accumulated actual selection differentials, declined with selection; the decline appeared to be slightly different for males than females. For both sexes combined, the realized h2 was 0.309+/-0.022 (SE), 0.268+/-0.033, 0.242+/-0.026, and 0.254+/-0.007, respectively, for Generations 1 to 10, 11 to 20, 21 to 30, and 1 to 30. Genetic increases in 16-wk BW in the F line were positively associated with BW at other ages (8, 20, and 24 wk of age and at 50% production), days from stimulatory lighting to production of the first egg, and egg weight. Genetic increases were negatively associated with egg production, intensity of lay (maximum and average clutch length and rate of lay), and hatch of fertile eggs. There was no significant relationship between 16-wk BW and total days lost from broodiness or fertility. The genetic changes in some correlated traits were not consistent in all generation intervals studied, indicating that the genetic correlation between the selected trait (16 wk BW) and the correlated trait changed with selection.

Animals↗

PubMed1988

Genetic markers in Sjögren's syndrome: the question of its genetic heterogeneity.

Genetic factors may be implicated in the causation of Sjögren's syndrome (SS) as shown by familial clustering of the disease and certain HLA associations. Non-HLA genetic markers in SS have not previously been studied in detail. In this study of 122 unrelated patients with various categories of SS and 104 control subjects, 29 genetic markers were studied (11 blood groups, 5 serum proteins and 13 red-cell enzymes). Almost all systems showed a considerable range of gene frequency among the various subgroups of patients with SS but only a few attained statistical significance (C3 and GPT). Multivariate (kinship) analysis, however, showed clear distinction between the subgroups of SS, suggesting that they are genetically distinct entities.

Alleles↗

PubMed2006

Inbreeding and reproduction in endangered ungulates: preservation of genetic variation through the Organization of Genetic Resource Banks.

There is a constant increase in the number of species suffering marked reductions in population size. This reduction in size and the lack of genetic flow may lead to a decrease in genetic variability and to matings between close relatives (i.e. inbreeding) with an ensuing reduction in fitness. It is thus important to understand the mechanism underlying the deleterious effects of inbreeding and to develop reproductive biotechnologies that will allow the reduction of inbreeding depression by facilitating gene exchange between populations. The study of three endangered species of gazelles, Cuvier's gazelle (Gazella cuvieri), Mohor gazelle (Gazella dama mhorr) and dorcas gazelle (Gazella dorcas neglecta) has revealed that inbreeding negatively affects several semen parameters (motility, sperm morphology, acrosome integrity). Semen cryopreservation has been achieved in the three species but success varies depending on the diluent employed and the level of inbreeding. Artificial insemination of Mohor gazelles have led to the birth of the first gazelle born using frozen-thawed semen but improvements are needed before this technology can be applied on a routine basis for the genetic management of the populations. Collection of oocytes after ovarian stimulation, followed by in vitro maturation, fertilization and culture has met with some initial success in the Mohor gazelle. These, together with other reproductive technologies, will offer an invaluable help in preserving the maximum of genetic diversity of these and related endangered ungulate species.

Animals↗

PubMed2006

Three hundred and thirty cycles of preimplantation genetic diagnosis for serious genetic disease: clinical considerations affecting outcome.

OBJECTIVE: To report on our experience with preimplantation genetic diagnosis (PGD) cycles performed for serious genetic disease in relation to the clinical factors affecting outcome. DESIGN: Retrospective review of data from a single centre. SETTING: Tertiary referral PGD centre in a London teaching hospital. METHODS: The PGD cycles included 172 cycles for chromosome rearrangements, 96 cycles for single-gene disorders and 62 cycles for X-linked disorders. In vitro fertilisation was the preferred method in chromosome rearrangement and X-linked cases, while intra cytoplasmic sperm injection was used in all single-gene disorders. Appropriate in situ hybridisation fluorescence probes were used in chromosome rearrangement and X-linked cases and polymerase chain reaction was used in single-gene disorders. All pregnancies were followed till delivery. MAIN OUTCOME MEASURE: Live birth rate per PGD cycle started. RESULTS: Eighty-six percent of cycles started (283) reached oocyte retrieval and 3743 eggs were collected, of which 2086 fertilised normally (55.7%). Two hundred and fifty cycles (76%) had embryos sutiable for biopsy on day 3 of in vitro culture, 1714 embryos were biopsied, and in 205 cycles (62%), there was at least one unaffected embryo available for transfer, resulting in 90 pregnancies, 68 clinical pregnancies and 58 live birth. The live birth rate was 18% per cycle started, 21% per egg retrieval and 28% per embryo transfer which significantly affected the live birth outcome. Woman age, number of eggs collected and achieving cryopreservation of surplus embryos had no statistically significant effect on treatment outcome. CONCLUSIONS: The live birth outcome of PGD cycles for serious genetic disorder is modest and is affected by the number of embryos genetically suitable for transfer.

Adult↗

PubMed2006

Genetically diverse group A streptococci from children in far-western Nepal share high genetic relatedness with isolates from other countries.

The genetic diversity of group A streptococci (GAS) throughout much of the world has not been adequately explored. To assess genetic variation among GAS in western Nepal, 120 noninvasive GAS, collected from eight different villages, were genetically characterized using emm typing, sof sequencing, and multilocus sequence typing (MLST). A high level of genetic diversity was observed among these isolates, with 51 genotypes based upon 51 multilocus sequence types (STs), 45 emm sequence types, and 28 sof sequence types. On the basis of shared ST-emm and sof-emm associations, 40 of the 51 genotypes were identical or highly related to genotypes characterized from locations outside of Nepal, even though most of the emm sequence and clonal types are rare among GAS within the United States. When analyzing all known STs highly related to Nepal STs, only one example of similar STs shared between a sof PCR-positive strain and a sof PCR-negative strain was observed. Since previous data indicate free exchange of MLST loci between sof-positive and sof-negative strains, there is possibly selection against the expansion of subclones resulting from horizontal transfers of sof or emm genes between sof-positive and sof-negative strains. All 45 emm types encountered in Nepal have also been documented from other countries. These data, together with data encompassing the past decade of emm type surveillance, support the possibility that most existing GAS emm types have been discovered. Similarly, since most (40/51) strain types were highly related to strains found elsewhere, it is likely that a major fraction of the existing GAS clonal complexes have been discovered.

Antigens, Bacterial↗

PubMed1997

RNAs from genetically distinct retroviruses can copackage and exchange genetic information in vivo.

Sequence analysis suggests that ancient recombination events may have occurred between genetically distinct retroviruses. An experimental system was utilized to explore the genetic interaction between different viruses. Moloney murine sarcoma virus and spleen necrosis virus are type C retroviruses that belong to different subgenera. With vectors containing packaging signals from these two viruses, DNA proviruses containing genetic information from both RNAs can be generated. This is the first experimental evidence to indicate that RNA from different retroviruses can copackage and exchange genetic information.

Genetic Vectors↗

PubMed1993

Ulcerative colitis: a genetically heterogeneous disorder defined by genetic (HLA class II) and subclinical (antineutrophil cytoplasmic antibodies) markers.

Newly described distinct associations of HLA class II genes with ulcerative colitis (UC) (DR2) and Crohn's disease (CD) (DR1/DQ5) provide strong evidence for genetic heterogeneity of susceptibility between these two forms of inflammatory bowel disease. A familial distribution of antineutrophil cytoplasmic antibodies (ANCAs, a subclinical marker of UC) in UC families has further implied the existence of heterogeneity within UC. To test the hypothesis that the heterogeneity within UC indicated by ANCAs has a genetic basis that resides within the HLA region, we studied 89 UC cases and an ethnically matched control group (n = 50). Serological and molecular typing techniques were applied to define HLA class II genes (DR, DQ). ANCAs were detected using an enzyme-linked immunosorbent assay, and positive values were confirmed by indirect immunofluorescence. We observed that ANCA-positive UC patients (n = 70) had a significantly increased frequency of DR2 compared with ANCA-negative controls (n = 46) (44% vs 22%, P = 0.01). In contrast, the frequency of DR2 in ANCA-negative UC cases (21%) was virtually identical to that in controls (22%, P = 0.9). Furthermore, the ANCA-negative UC patients had an increase in the DR4 allele compared with ANCA-positive UC (P = 0.004). Thus, with the combination of a subclinical marker (ANCAs) and molecular genetic markers, genetic heterogeneity has been demonstrated within UC: ANCA-positive UC associated with DR2, and ANCA-negative UC likely associated with DR4.

Adult↗

PubMed1991

Clinical genetics and genetic counseling in Alzheimer disease.

Because of growing evidence for genetic causes of Alzheimer disease, clinicians are often asked about risks for this disorder among relatives of patients. This paper briefly reviews the evidence for genetic and other causes of Alzheimer disease, including specifically its typical late-onset variant. Several recent developments in the molecular genetics of early-onset Alzheimer disease are described briefly. These findings, however, may not apply to more typical, late-onset Alzheimer disease. Genetic studies of the latter disorder are complicated by the censorship of any inherited predisposition to disease by death from other causes. Hence, heritable disease may be apparent only in families with large numbers of elderly relatives at risk. Relying on empiric observations of risk among relatives from several recent studies of pooled Alzheimer families, curves are presented describing theoretic age-specific risks in relatives of patients and unaffected controls. Real (current) lifetime risks of Alzheimer disease are then estimated by modification of the theoretic figures with corresponding current age-specific mortality characteristics of the U.S. population. The lifetime incidence among relatives of patients with Alzheimer disease is estimated to be 19%, or three to four times the risk among control relatives. Because both mortality of and risk for Alzheimer disease change rapidly with advancing age, it may be possible to reduce the current morbidity from Alzheimer disease by 50% if onset can be postponed by only 5 years.

Age Factors↗

PubMed1998

[Genetic diagnosis of IVF embryos: preliminary results from 'preimplantation genetic diagnoses' in the Netherlands].

Preimplantation genetic diagnosis (PGD) is a very early form of genetic testing. It involves testing one or two cells taken from a recent embryo of eight cells produced by in vitro fertilization, and selective transfer of genetically normal embryos. So far in the Academic Hospital Maastricht, the Netherlands, 20 couples have undergone PGD, resulting in 6 ongoing pregnancies (one twin pregnancy). In three women the indications for PGD were: cystic fibrosis, sex-linked Pelizaeus-Merzbacher disease and chromosomal translocation, respectively. In the Netherlands PGD is only allowed if there is a high risk of a serious genetic disease. PGD can be carried out in Maastricht for: cystic fibrosis, sex-linked diseases, chromosomal abnormalities, fragile X syndrome, spinal muscular atrophy and myotonic dystrophy. The advantage of PGD is that it excludes the necessity of a therapeutic abortion. Disadvantages ages are the requirement of in vitro fertilization, which has only a 15-20% pregnancy rate, and the experimental nature of the PGD procedure. To date, about 200 children have been born worldwide following PGD.

Adult↗

PubMed2001

The influence of genetic background on spontaneous and genetically engineered mouse models of complex diseases.

In recent years, the use of genetically altered mice as models of complex human disease has revolutionized biomedical research into the genetics of disease pathogenesis and potential therapeutic interventions. Whether a mouse expresses a spontaneous or induced mutation, it is critical to remember that the observed phenotype is not always the direct result of the genetic alteration. The author points out the importance of considering the genetic background of the strain used to create these important models.

Animals↗

PubMed2001

[First attempts in preimplantation genetic diagnosis: genetic analysis].

Preimplantation genetic diagnosis is a new approach for the prevention of genetic disorders, which provides a healthy pregnancy avoiding the need for its possible termination. The combination of in vitro fertilization techniques and single cell molecular genetic diagnosis allows only unaffected embryos to be selected for transfer to the uterus. It is an acceptable alternative of prenatal diagnosis for certain couples. Here we report our first attempts in the application of fluorescent PCR for sex determination and the detection of the delta-F508 mutation in human blastomeres. We modelled clinical PGD situations as we performed sex determination on 23 preembryos. Sex determination was successful is 20 preembryos (83%). We performed the detection of the delta-F508 mutation on 23 preembryos, which was successful in 20 preembryos (87%). Our experience suggests, that the established fluorescent PCR analysis is a reliable method for PGD, which enables us to apply it for clinical preimplantation genetic diagnosis.

Blastomeres↗

PubMed1979

[Population genetics of the population of the northern European RSFSR. III. Demographic and genetic characteristics of two rural communities of the Pinezhskii District of the Arkhangel'sk Region].

The paper deals with the distribution of genetic markers (systems ABO, Rh, Hp, PTC) and a number of phenotyping traits (folding of arms, hand clasping, tongue rolling, right- and left-handedness, the type of ear lobe, the types of dermatoglyphics patterns) in the inhabitants of 5 villages in the Pinezhsky district of the Arkhangelsky region of the RSFSR. The data presented in this work were obtained in the course of examination of over 900 persons. Among the systems analysed there was a statistically significant deviation from Hardy-Weinberg's equlibrium. It took place in two the least villages. In one case--for ABO blood groups, in another--for Hp system. There are an interesting fact of the excess of heterozygotes 2-1 and some excess of the group 0. Statistically significant differences between villages were shown for four genetic systems. Data on migrations, distribution of gene frequencies and estimated genetic and phenotype distances between villages of the same village community and between two communities suggest, that each village community can be considered as separate subdivided population. Considering the uniformity of the environmental pressure in the region examined, the heterogeneity of the population studied is apparently associated with a random genetic drift.

Blood Group Antigens↗

PubMed2006

[The role of the genetics history in genetics teaching].

The research of the scientific history and development status reflect the science and technology level of a nation. The genetic history is one of the branches of the life science and the 21st century is life science century. The genetics history in the teaching of genetics not only can help students get familiar with the birth and development of genetics, but also enhance their thinking ability and scientific qualities. The roles and approaches of teaching are discussed in this paper.

China↗

PubMed1991

[Clinico-genetic aspects of retinoblastoma. II. Genetic consultation in 35 families with retinoblastoma].

The author presents a genealogical analysis of 35 families suffering from retinoblastoma and uses the results of the aetiological diagnosis to assess more accurately the ratio of heredity in the aetiology of retinoblastoma. All families received genetic consultation and the family-history was studied from the genetic and clinical aspect. The authors discuss different situations encountered during genetic consultations and outline new possibilities of screening of retinoblastoma by using discoveries of molecular genetics.

Eye Neoplasms↗

PubMed1987

The economics of clinical genetics services. II. A time analysis of a medical genetics clinic.

In a time-and-reimbursement analysis of our clinical genetics service, we documented (1) the time spent by professionals and staff in serving families before, during, and after the clinic visit; (2) the charges and reimbursement for the services provided; and (3) the relationship between income from clinical practice and the personnel costs of the clinic. We found that newly referred and returning families required 7.1 and 4.0 h, respectively. Average collections for professional services were +135 (+19/h) for new families and +49 (+12/h) for returning families. Income from clinical practice covered 37% of the clinical portion of personnel costs. These results indicate that cognitive clinical genetics services are labor intensive, yield low payments per service hour, and are not financially self-supporting. To improve the economic status of genetics clinics, administrators might consider rendering services more efficiently; increasing charges for services; billing for all services provided to all family members; billing for all genetics professionals, including counselors and social workers; and requesting payment at the time of service.

Cost-Benefit Analysis↗