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Copy number variation (CNV) is a phenomenon in which sections of the genome are repeated and the number of repeats in the genome varies between individuals. [1] Copy number variation is a type of structural variation: specifically, it is a type of duplication or deletion event that affects a considerable number of base pairs. [2]
Copy number analysis is the process of analyzing data produced by a test for DNA copy number variation in an organism's sample. One application of such analysis is the detection of chromosomal copy number variation that may cause or may increase risks of various critical disorders.
Gains: A copy number gain represents the gain of genetic material. If the gain is of just one additional copy of a segment of DNA, it may be called a duplication (Fig 4). If there is one extra copy of an entire chromosome, it may be called a trisomy. Copy number gains in germline samples may be disease-associated or may be a benign copy number ...
If an extra copy is present in the test sample, the signals are expected to be 1.5 times the intensities of the respective probes from the reference. If only one copy is present the proportion is expected to be 0.5. If the sample has two copies, the relative probe strengths are expected to be equal.
However, the amount of DNA or the number of genes can also increase within an organism through gene duplication, a major mechanism through which new genetic material is generated during molecular evolution. Common sources of gene duplications include ectopic recombination, retrotransposition event, aneuploidy, polyploidy, and replication slippage.
Homogeneously staining regions (HSRs) are chromosomal segments with various lengths and uniform staining intensity after G banding.This type of aberration is also known as Copy Number Gains or Amplification.
Comparative genomic hybridization (CGH) is a molecular cytogenetic method for analysing copy number variations (CNVs) relative to ploidy level in the DNA of a test sample compared to a reference sample, without the need for culturing cells.
On the other hand, dPCR has a higher precision and has been shown to detect differences of less than 30% in gene expression, distinguish between copy number variations that differ by only 1 copy, and identify alleles that occur at frequencies less than 0.1%. [14] [5]