Define elucidating

In addition to conventional chromosome markers, morphological differentiation may occur on the basis of the position of centromere (primary constriction), secondary constriction, relative arm ratio.Chromosome banding provide further linear differentiation of chromosomes, facilitating differentiation between the morphologically similar chromosome linkage groups within the karyotype.To cite a case example, randomly selected 202 BAC clones of With the aid of FISH techniques, it has now been possible to physically visualize genes and DNA sequences under a microscope on extended DNA fibers (EDFs) from interphase nuclei.In wheat itself EDF fibers could be obtained even from metaphase chromosomes [].An index called Chromosome “Dispersion Index” depicting statistical gradient of centromere position within the karyotype to facilitate finer differentiation of closely related karyotypes falling within the same “asymmetry” class of Stebbins was developed by Lavania and Srivastava [], and has been widely used by the cytotaxonomists.The power of karyotype analysis expanded in late 1960s with the development of banding techniques, including fluorescence and Giemsa staining, reviewed in Lavania [].On human chromosomes, single copy sequences as small as 1 kb could be routinely detected by the standard FISH technique.But in wheat it is difficult to locate even 10 kb sequences even when amplification of FISH signals is applied to improve efficiency and realize higher FISH resolution.

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The information about the exact physical location of agronomically important genes could be useful for a breeding program as well as understanding of the organization of cereal genomes.In order to elucidate karyotypic differentiation vis-à-vis evolutionary specialization, Stebbins [] provided the classification of karyotypes into 12 categories, ranging from an extreme symmetrical to an asymmetrical karyotype, based on relative proportions of chromosome morpho-types in a given karyotype.Several karyomorphological arrangements elucidating karyotypic details have since been provided [].Large genomic clones such as lambda phages, cosmids, BACs and PACs could be successfully used to realize low copy localization, since large amount of repeated sequences contained in them would facilitate homologous hybridization, signal detection of which would be suppressed by competitive hybridization with unlabelled -1 DNA or total genomic DNA.This would enable the unique sequences of interest to be expressively detected.

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