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At least 307 records · Page 17Linked to original sources
PubMed2001

Experimental approaches to the determination of genetic variability.

Toxicology is concerned with the interaction between xenobiotics and biological molecules directly or indirectly coded in the DNA, and can be regarded as a branch of genetics. There is genetic variation in these interactions, which has important implications for risk assessment and because it can be used as a tool in studying toxic mechanisms. The genetics of susceptibility can be studied by forward or reverse genetics. Forward genetics involves working from an observed phenotype such as susceptibility to a particular xenobiotic and identifying the susceptibility genes. Often, this involves mapping and identifying quantitative trait loci, as most toxic responses have a polygenic mode of inheritance. The use of inbred strains is almost essential. Reverse genetics involves starting with a known genetic polymorphism and determining its effects on the response to xenobiotics. Studies of 'knockout' animals are a good example, although there are many naturally occurring polymorphisms that may affect toxic responses. In both cases, care has to be taken to ensure that the genetic background is carefully controlled in any comparison between animals thought to be carrying susceptible and resistant alleles.

Animals↗
PubMed2004

A structured mutant population for forward and reverse genetics in Barley (Hordeum vulgare L.).

Two large-scale ethylmethanesulfonate (EMS) mutant populations from barley (Hordeum vulgare L.) cv. Optic have been developed to promote both forward and reverse genetics in this crop. Leaf material and seed from approximately 20 000 M(2) plants were individually harvested, freeze-dried and archived. DNA was isolated from 9216 plants from the 20 and 30 mm EMS treatments and assembled into 1152 eight-plant pools. To facilitate PCR-based mutation scanning an approach has been employed that combines cleavage of heteroduplexes using the Cel nuclease (Cel I), post-cleavage intercalating dye labeling and the subsequent detection of cleaved products on a Transgenomic WAVE-HS. The populations were evaluated by screening for induced mutations in two genes of interest and the induced mutations were validated by sequence analysis. To enhance the screening process, 12-16 M(3) progeny from each of the M(2) plants were assessed for visible phenotypes and the data entered into a web accessible database (http://bioinf.scri.sari.ac.uk/distilling/distilling.html).

Base Pair Mismatch↗
PubMed2003

Forward & reverse chemical genetics using SPOS-based combinatorial chemistry.

Combinatorial chemistry is being applied to diverse problems in the biological and pharmaceutical sciences. This review will describe an emerging application called "chemical genetics" or "chemical genomics" - genetics and genomics are often used interchangeably in this context. In forward chemical genomics, chemical libraries are tested in living systems to discover compounds that cause a desirable effect. Subsequently, the protein target is identified using various biochemical and molecular biological tools. By this method, we gain insights into the inner workings of life, and indeed, in some forms this has been the path by which most of the pharmacopoeia was discovered. In reverse chemical genetics, proteins of interest are used to probe compound collections, and those compounds that bind the proteins of interest are used to treat living systems and observed for interesting biological responses. Plausible biological roles of these proteins are inferred from the effects of the compounds because they are assumed to generally inhibit, or more rarely, stimulate, the protein's functions. Interestingly, the reverse genetic approach is emerging as the leading model for drug discovery today. Different methods and cases will be described to illustrate forward and reverse paradigms, including those developed in the author's laboratory.

Combinatorial Chemistry Techniques↗
PubMed1994

Psychiatric genetics: research challenges and pathways forward.

Lessons from past psychiatric genetic research, together with key issues in psychiatry requiring genetic investigation, are reviewed in order to consider the implications for the ways forward. It is argued that traditional quantitative genetics needs to use a combination of twin, adoptee, and family strategies, to examine continuities and discontinuities in psychopathology between childhood and adult life, to compare dimensions and categories, to employ adequate conceptualization and measurement of disorders, to use statistical techniques based on latent constructs, to use biological trait indicators where possible, to examine risk factors as well as diseases, to include good measures of postulated environmental risk variables, to study the interplay between genes and environment, and to study the key assumptions underlying genetic strategies. Molecular cytogenetics needs to consider both the general and specific psychopathological risks associated with chromosome abnormalities and to examine the mechanism involved, to examine the role of submicroscopic chromosomal deletions and of mitochondrial disorders, and to investigate the mechanisms involved in trinucleotide repeat amplifications that take place during intergenerational transmission. Molecular genetics needs to make greater use of smaller pedigrees in view of the concerns over phenotypic definition and genetic heterogeneity in very large extended dense pedigrees, to use sib-pair designs in view of the likelihood that most psychiatric disorder will prove to be multifactorial, to combine association strategies with linkage analyses, to pay careful attention to the definition of phenotypes in probands, to remain in close touch with other branches of biological psychiatry, and to make effective use of collaboration between centers. To date, transgenic models have had a rather limited application in psychiatry but, despite their difficulties, they are likely to provide an underpinning for gene therapy in disorders where that seems feasible.

Genetic Heterogeneity↗
PubMed1999

The circadian system of Arabidopsis thaliana: forward and reverse genetic approaches.

It is now widely accepted that autoregulatory circuits involving transcription/translation of clock genes form the molecular basis of the endogenous circadian clock in different organisms. In Arabidopsis thaliana, the RNA-binding protein AtGRP7 (Arabidopsis thaliana glycine-rich protein) has been identified as part of a negative-feedback loop through which AtGRP7 regulates the circadian oscillations of its own transcript. Experimental evidence indicates that this feedback loop also is influenced by another oscillator. Support for this hypothesis comes from the characterization of the clock mutant toc1 (timing of cab expression) and the recent isolation of two candidate clock molecules, LHY (late elongated hypocotyl) and CCA1 (circadian clock associated). TOC1, as well as the LHY and CCA1 oscillatory feedback loops, influence several rhythmic physiological and molecular processes in Arabidopsis, including cyclic Atgrp7 gene expression. We discuss the features of these feedback loops with relation to the organization of the circadian system in Arabidopsis.

Arabidopsis↗
PubMed1983

Rate of induced forward mutation at 3 genetic loci in Salmonella typhimurium.

The rate of forward mutation to 8-azaguanine, 5-fluorouracil and azetidine carboxylic acid resistance was measured in Salmonella typhimurium following treatment with 18 chemical mutagens. Although the absolute frequency of both spontaneous and chemically-induced mutation was different at the markers scored, the 3 selection systems were found to be equisensitive: each system produced a statistically significant response at approximately the same mutagen concentration. This result suggests that in Salmonella the target size present in a given forward mutation assay is sufficiently large to approximate the level of mutation occurring elsewhere in the chromosome in sections of DNA of similar size.

DNA, Bacterial↗
PubMed2002

Psychiatric genetics: the case of single gene disorders.

Quantitative and molecular genetics have made important developments in the last three decades. There is increasing evidence of the role of heredity in the field of neuropsychiatric disorders in children. So far, only a few pathways between genes and behaviour have been unravelled. Quantitative genetics puts polygenic inheritance models forward. Molecular genetic research based on these models seems promising, but until now has provided only a limited explanation for the variance in the studied neuropsychiatric disorders. In these models the complexity of the expression of a single gene grows exponentially with the number of genes involved. Consequently, research on the gene-phenotype relationships and phenotypical variability in such models is extremely complex.The candidate gene approach, in which the gene-phenotype pathway of a single gene is studied, is more manageable, and in our opinion essential in understanding multiple gene models. We discuss recent findings in the field and their relevance for neuropsychiatric phenotypes. Single gene defects will only explain a part of the range of neuropsychiatric disorders in children, but the evidence that this approach can generate may help to clarify neuropsychiatric phenotypes. The discovery of single gene disorders in subgroups of subjects with a neuropsychiatric phenotype may result in new perspectives for their treatment.

Autistic Disorder↗
PubMed2006

Genetic screens for mutations affecting development of Xenopus tropicalis.

We present here the results of forward and reverse genetic screens for chemically-induced mutations in Xenopus tropicalis. In our forward genetic screen, we have uncovered 77 candidate phenotypes in diverse organogenesis and differentiation processes. Using a gynogenetic screen design, which minimizes time and husbandry space expenditures, we find that if a phenotype is detected in the gynogenetic F2 of a given F1 female twice, it is highly likely to be a heritable abnormality (29/29 cases). We have also demonstrated the feasibility of reverse genetic approaches for obtaining carriers of mutations in specific genes, and have directly determined an induced mutation rate by sequencing specific exons from a mutagenized population. The Xenopus system, with its well-understood embryology, fate map, and gain-of-function approaches, can now be coupled with efficient loss-of-function genetic strategies for vertebrate functional genomics and developmental genetics.

Animal Diseases↗