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Successful experiments involving the production of transgenic mice by pronuclear microinjection are currently limited by low efficiency of random transgene integra­tion into the mouse genome. Furthermore, not all transgenic mice express integrated transgenes, or in other words are effective as functional transgenic mice expressing the desired product of the transgene, thus allowing accomplishment of the ultimate experimental goal - in vivo analysis of the function of the gene or gene network. The purpose of this review is to look at the current state of transgenic technology, utiliz­ing a pronuclear microinjection method as the most accepted way of gene transfer into the mouse genome.
It has been hypothesized that developmental stability is increased at higher levels of genetic variability (heterozygosity) in animals. However, the existence of this relationship is questionable for homeotherms in general and mammals in particular. The difference between the sides of a bilateral character in an individual is a measure of fluctuating asymmetry that can be used as a measure of the developmental stability of mammals. Increased developmental stability should result in a greater degree of similarity between the right and left side of the body even though environmental variability would tend to increase the differences between right and left sides of the body. It is necessary to separate the effects of the three types of asymmetry so that an accurate estimate of the variance attributable to fluctuating asymmetry can be made. In addition, many early studies of asymmetry in poikilotherms used meristic characters (such as scale counts), and these types of characters are not easily studied in mammals. Mammals, because of their precise regulation of body temperature show little phenotypic effect of environmental variability, and thus may exhibit low absolute levels of asymmetry. Mammals may also be able to reduce the level of asymmetry during their prolonged intrauterine development and juvenile growth period. The literature is reviewed relative to relationships between genetic variation and asymmetry in mammals. Hypotheses are reviewed as they relate to the relationship between fluctuating asymmetry and heterozygosity observed in previous studies. Finally, recommendations are put forth regarding the design and interpretation of future research into the relationship between developmental homeostasis and genetic variability.
Birth defects (BD) surveillance using international standards was introduced in Ukraine by a network of five BD centers located in northwestern, central and southern regions. BD centers provide resources to access current and comprehensive information and to nurture partnerships with physicians, administrators, parental support groups, educators, and humanitarian assistance organizations. One outcome was the vigorous and popular website International BD Information Systems (IBIS). The network is now incorporated as OMNI-Net Ukraine. The program has documented high prevalence rates of neural tube defects (NTD); fetal alcohol effects (FAE); and idiopathic developmental retardation among orphans that prompted prevention and amelioration initiatives. Further program objectives include: universal folic acid flour fortification, as recommended by the Ukrainian Academy of Medicine; continued research on methods to reduce FAE in collaboration with partners from California; opening other early infant stimulation centers funded by local authorities, modeled on those in Rivne and Lutsk; and linking BD prevention with bioethical considerations, which is a topic of interest in Ukraine in part enhanced by the effects of Chornobyl.
Karyotypic polymorphism of five taxa of the rodent genus Rhipidomys from the Brazilian Amazon and Cerrado biomes was analysed. Rhipidomys nitela Thomas, 1901 from Amazon has 2n = 48, FN = 68. The other species, all have 2n = 44, but can be separated into two groups, one with high FNs (76, 80) and the other with low FNs (48, 52). Two cytotypes of R. mastacalis (Lund, 1840) with high FNs were trapped in four localities of the Cerrado, showing 19 and 17 biarmed autosomes, respectively. A low FN (48) was observed in R. leucodactylus (Tschudi, 1844) in two localities of the Cerrado and FN = 52 in one locality in the Cerrado and the Amazon. All taxa with 2n = 44 have a medium-sized acrocentric X chromosome and a small Y. Rhipidomys nitela is different from the species with 2n = 44 by presenting a heterochromatic short arm of the X chromosome. In all karyotypes analysed, the nucleolus organizer regions were located in the short arms of two to six pairs and the (T2AG3)n telomeric probes hybridized in situ in both the short and long arms of all pairs of the karyotypes.
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