|
| ||
|
|
||
Chromosome Regions (chromosome + regions)
Selected AbstractsThe genetics of autismACTA PSYCHIATRICA SCANDINAVICA, Issue 6 2001M. Lauritsen Objective: To review systematically the empirical evidence for the involvement of genetic risk factors in infantile autism. Method: We aimed at including all relevant papers written in English. We conducted a Medline search in September 2000. In addition we searched the reference lists of related papers. Results: A relatively small number of reports including family and twin studies, comorbidity, cytogenetic and molecular genetic studies were reviewed. Conclusion: As well family, twin, cytogenetic and molecular genetic studies supported the importance of genetic risk factors in infantile autism. In most individual cases probably at least a few gene variants simultaneously determine the genetic risk. Presently the most interesting chromosome regions concerning the aetiology of autism are chromosomes 7q31,35, 15q11,13 and 16p13.3 which have been suggested by different lines of genetic research. [source] The role of hybridization in evolutionMOLECULAR ECOLOGY, Issue 3 2001N. H. Barton Abstract Hybridization may influence evolution in a variety of ways. If hybrids are less fit, the geographical range of ecologically divergent populations may be limited, and prezygotic reproductive isolation may be reinforced. If some hybrid genotypes are fitter than one or both parents, at least in some environments, then hybridization could make a positive contribution. Single alleles that are at an advantage in the alternative environment and genetic background will introgress readily, although such introgression may be hard to detect. ,Hybrid speciation', in which fit combinations of alleles are established, is more problematic; its likelihood depends on how divergent populations meet, and on the structure of epistasis. These issues are illustrated using Fisher's model of stabilizing selection on multiple traits, under which reproductive isolation evolves as a side-effect of adaptation in allopatry. This confirms a priori arguments that while recombinant hybrids are less fit on average, some gene combinations may be fitter than the parents, even in the parental environment. Fisher's model does predict heterosis in diploid F1s, asymmetric incompatibility in reciprocal backcrosses, and (when dominance is included) Haldane's Rule. However, heterosis arises only when traits are additive, whereas the latter two patterns require dominance. Moreover, because adaptation is via substitutions of small effect, Fisher's model does not generate the strong effects of single chromosome regions often observed in species crosses. [source] Genome analysis and gene expression profiling of neuroblastoma and ganglioneuroblastoma reveal differences between neuroblastic and Schwannian stromal cellsTHE JOURNAL OF PATHOLOGY, Issue 3 2005Simona Coco Abstract Neuroblastic tumours are a group of paediatric cancers with marked morphological heterogeneity. Neuroblastoma (Schwannian stroma-poor) (NB-SP) is composed of undifferentiated neuroblasts. Ganglioneuroblastoma intermixed (Schwannian stroma-rich) (GNBi-SR) is predominantly composed of Schwannian stromal (SS) and neuroblastic (Nb) cells. There are contrasting reports suggesting that SS cells are non-neoplastic. In the present study, laser capture microdissection (LCM) was employed to isolate SS and Nb cells. Chromosome 1p36 deletion and MYCN gene amplification were found to be associated in two out of seven NB-SPs, whereas no abnormalities were observed in five GNBi-SRs. In some cases, loss of heterozygosity (LOH) at 1p36 loci was detected in Nb cells but not in the bulk tumour by LCM; furthermore, LOH was also identified in both SS and tumour tissue of a GNBi-SR. DNA gain and loss studied by comparative genomic hybridization were observed at several chromosome regions in NB-SP but in few regions of GNBi-SR. Finally, gene expression profiles studied using an oligo-microarray technique displayed two distinct signatures: in the first, 32 genes were expressed in NB-SP and in the second, 14 genes were expressed in GNBi-SR. The results show that NB-SP is composed of different morphologically indistinguishable malignant cell clones harbouring cryptic mutations that are detectable only after LCM. The degree of DNA imbalance is higher in NB-SP than in GNBi-SR. However, when the analysis of chromosome 1p36 is performed at the level of microdissection, LOH is also observed in SS cells. These data provide supportive evidence that SS cells have a less aggressive phenotype and play a role in tumour maturation. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [source] A genome scan for quantitative trait loci affecting three ear traits in a White Duroc × Chinese Erhualian resource populationANIMAL GENETICS, Issue 4 2009J. Ma Summary Chinese Erhualian pigs have larger and floppier ears compared with White Duroc pigs (small, half- or fully-pricked ears). To identify quantitative trait loci (QTL) for ear weight and area as well as erectness, a genome-wide scan with 194 microsatellites was performed in a White Duroc × Chinese Erhualian resource population (>1000 F2 animals). Twenty-three genome-wide significant QTL and 12 suggestive QTL were identified. All QTL for ear erectness and size detected in two previous studies, bar two on SSC6 and 9, were confirmed here. The 1% genome-wide significant QTL at 70 cM on SSC5 and at 58 cM on SSC7 have profound and pleiotropic effects on the three ear traits, with Erhualian alleles increasing weight and area but decreasing erectness. Notably, the 95% confidence interval of the QTL for weight and area on SSC7 spanned only 3 cM. New QTL reaching 1% genome-wide significance were found on SSC8 (at 37 cM) for all three ear traits, on SSC4 and 16 for weight and area, and on SSCX for area. Unexpectedly, Erhualian alleles at these loci were associated with lighter and smaller or erect ear. Some new suggestive QTL were also found on other chromosome regions. Almost all the QTL for weight and area had essentially additive effects, while the QTL for erectness on SSC2, 5 and 7 showed not only additive effects but also partial dominance effects of Erhualian alleles. The two most significant QTL on SSC7 and SSC5 could be promising targets for fine mapping and identification of the causative mutations. [source] Identification of candidate genes for schizophrenia based on natural resistance to infectious diseasesACTA NEUROPSYCHIATRICA, Issue 3 2003James S Brown Jr Background:, Identification of candidate genes for schizophrenia may be more successful than genome screens as the latter have not found consistent linkages. Objective:, To assist in the gene search, a model of schizophrenia based on resistance to infectious diseases, rather than susceptibility, is proposed. The theory blends the geography of schizophrenia with the assumption that genes that cause schizophrenia likely evolved and persist from selection pressure. The theory includes the notion that schizophrenia enhances biological survival at the cost of psychological and social functioning. Method:, To demonstrate the utility of using this model, the Medline literature was searched for resistance genes, mostly identified in mice. Results:, Based on homologous locations in the human genome, these resistance genes are shown to be located in human chromosome regions linked significantly, in at least one genome screen, with schizophrenia or some physiologically related function or condition associated with schizophrenia. Conclusions:, The infectious disease resistance theory of schizophrenia is offered as a viable model for understanding the origins of schizophrenia. The theory also allows for the inclusion of persistent infections, seasonal variability and translational pathophysiology to contribute to the etiology of schizophrenia. [source] | |||||||||||||