structure of an organisms chromosomes
The structure of an organisms chromosomes can have striking variation among individuals including Show more The structure of an organisms chromosomes can have striking variation among individuals including insertions deletions inversions transpositions and copy-number variation. Structural variation of a chromosome has been shown to contribute to diseases (Helbig et al. 2014; Ramos-Quiroga et al. 2014). Additionally structural variation has been shown to play a role in the evolution of the genome (Sudmant et al. 2013) and consequently of the organism itself. Despite these findings relatively little is known about the function of most structural variation and its impact on organisms such as the influence on gene expression (Harewood et al. 2012). The ability to map the structure and numerous functional units that comprise a chromosome has improved along with recent technological advancements. The traditional method to analyze chromosome structural variation was until recently by array comparative genome hybridization (aCGH). aCGH analyzes the change in the fluorescence level of DNA compared to reference DNA in order to detect copy-number variation (Graubert et al. 2007). The control DNA in aCGH studies is typically derived from a reference genome of a single animal of the species. In medical genetics the sample DNA could be prepared from a tumor biopsy whereas the reference DNA could be derived from the patients unaffected cells. aCGH studies remain difficult to reproduce and cannot detect other important structural variations that do not alter the copy number. The growing demand for high-throughput sequencing has continued to reduce the cost and improve the efficiency of whole-genome sequencing using next-generation sequencing methods. It is now practical to sequence the entire genome of a particular laboratory strain or an individual animal to assay for structural variation of chromosomes without the need for a reference genome. Next-generation sequencing has been used to sequence laboratory mouse strains and map the structural variation of each individual strain without bias (Simon et al. 2013; Sousa et al. 2013). The resulting structural variation observed was significantly higher than expected based upon previous methods. In fact there were ten times more structural variants detected than there were single-nucleotide polymorphisms accounting for 1% of the entire mouse genome. In the future the most complex structural architecture will likely require improvements to existing assembly software; however sequencing improvements continue to mitigate the issue by increasing the length of individual reads. Select the statements that describe the advantages of next-generation sequencing over aCGH for mapping chromosome structural variation. This is WAAAY too advanced for me and my insturctor hasnt provided any information on this. If you could even explain a tiny bit it would be greatly appreciated!! Show less
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