Archana Sharma

Bio: Archana Sharma is an academic researcher from University of Calcutta. The author has contributed to research in topics: Sister chromatid exchange & Chromosome. The author has an hindex of 35, co-authored 234 publications receiving 5783 citations. Previous affiliations of Archana Sharma include Laval University.

Molecular hybridisation in situ

Abstract: Publisher Summary This chapter illustrates the molecular hybridization of chromosomal structure in situ. The principle of the in situ technique is based on the use of pure labeled nucleic acid fractions obtained from the in vivo state or prepared from complementary DNA sequences in vitro and their hybridization with previously denatured DNA of the chromosomes in situ. The detection of a particular DNA sequence in a chromosome is dependent principally on two important factors: (1) the sensitivity of detection and (2) the sequence complexity of DNA. The strength of detection depends on the amount of radioactivity and sensitivity of the autoradiographic procedure. Reassociation of DNA, implying restoration of the duplex is, in effect, the reverse process and requires a stronger salt concentration and lower temperature than that required for denaturation. There are various ways of measuring the rate of reassociation, the most convenient method being detection of fall in absorbance at 260 nm. For hybridization with complementary RNA, competition among complementary strands of DNA is also to be taken into account. It is not possible with the existing techniques to immobilize completely the complementary strands as done in case of in vitro techniques. For the in situ technique, in general, the ionic strength, the nucleic acid concentration, the temperature, and the period of incubation should be determined for each material, and the conditions are more or less identical to those needed for filter hybridization.

Isolation and extraction of nuclei, chromosomes and chromosome components

Abstract: Publisher Summary This chapter focuses on the isolation and extraction of nuclei, chromosomes, and chromosome components. The primary requisite for the extraction of nuclei is to isolate them in normal condition in adequate amounts and to keep the chromatin in an undamaged state. Several factors control the success of isolation, of which low temperature, medium, method of homogenization, pH, and divalent cations are most important and should be suitably adjusted for each tissue. The isolation procedure may be direct or indirect. In the former procedure, the nucleus is isolated directly from the cytoplasm with the aid of a micromanipulator and is observed under a microscope. The procedures for isolation are, however, not free from limitations. The principal disadvantage lies in the methodology for separation and the liquids needed for suspension. Even with weak solvents, there is the possibility of decomposition of sensitive compounds, adsorption of cytoplasmic contents by the nucleus, and elimination or diffusion of some nuclear components. In spite of these limitations, isolation techniques enable a worker to handle nuclei and chromosomes directly in the laboratory, permitting correct analysis of components.

Haptoglobin phenotypes in a group of mental retardates

Abstract: Sera from selected cases of mental retardates were studied for haptoglobin phenotypes (Hp) on polyacrylamide disc gel electro phoresis No significant alteration in the gene frequencies was observed from the normal control populations in Eastern India. However, a few cases had abnormal patterns which could not be attributed to external factors. An individual with idiopathic mental retardation showed the presence of an Hp° allele, which may have arisende novo.

The Effects of Plant Flavonoids on Mammalian Cells:Implications for Inflammation, Heart Disease, and Cancer

Abstract: Flavonoids are nearly ubiquitous in plants and are recognized as the pigments responsible for the colors of leaves, especially in autumn. They are rich in seeds, citrus fruits, olive oil, tea, and red wine. They are low molecular weight compounds composed of a three-ring structure with various substitutions. This basic structure is shared by tocopherols (vitamin E). Flavonoids can be subdivided according to the presence of an oxy group at position 4, a double bond between carbon atoms 2 and 3, or a hydroxyl group in position 3 of the C (middle) ring. These characteristics appear to also be required for best activity, especially antioxidant and antiproliferative, in the systems studied. The particular hydroxylation pattern of the B ring of the flavonoles increases their activities, especially in inhibition of mast cell secretion. Certain plants and spices containing flavonoids have been used for thousands of years in traditional Eastern medicine. In spite of the voluminous literature available, however, Western medicine has not yet used flavonoids therapeutically, even though their safety record is exceptional. Suggestions are made where such possibilities may be worth pursuing.

Genome duplication in the teleost fish Tetraodon nigroviridis reveals the early vertebrate proto-karyotype

Abstract: Tetraodon nigroviridis is a freshwater puffer fish with the smallest known vertebrate genome. Here, we report a draft genome sequence with long-range linkage and substantial anchoring to the 21 Tetraodon chromosomes. Genome analysis provides a greatly improved fish gene catalogue, including identifying key genes previously thought to be absent in fish. Comparison with other vertebrates and a urochordate indicates that fish proteins have diverged markedly faster than their mammalian homologues. Comparison with the human genome suggests ∼900 previously unannotated human genes. Analysis of the Tetraodon and human genomes shows that whole-genome duplication occurred in the teleost fish lineage, subsequent to its divergence from mammals. The analysis also makes it possible to infer the basic structure of the ancestral bony vertebrate genome, which was composed of 12 chromosomes, and to reconstruct much of the evolutionary history of ancient and recent chromosome rearrangements leading to the modern human karyotype.

The genome sequence of the filamentous fungus Neurospora crassa

Abstract: Neurospora crassa is a central organism in the history of twentieth-century genetics, biochemistry and molecular biology. Here, we report a high-quality draft sequence of the N. crassa genome. The approximately 40-megabase genome encodes about 10,000 protein-coding genes—more than twice as many as in the fission yeast Schizosaccharomyces pombe and only about 25% fewer than in the fruitfly Drosophila melanogaster. Analysis of the gene set yields insights into unexpected aspects of Neurospora biology including the identification of genes potentially associated with red light photobiology, genes implicated in secondary metabolism, and important differences in Ca21 signalling as compared with plants and animals. Neurospora possesses the widest array of genome defence mechanisms known for any eukaryotic organism, including a process unique to fungi called repeat-induced point mutation (RIP). Genome analysis suggests that RIP has had a profound impact on genome evolution, greatly slowing the creation of new genes through genomic duplication and resulting in a genome with an unusually low proportion of closely related genes.