Vergelijking van kopienummervariaties en SNP's

Genomic variations such as addition or deletion of segments of DNA are commonly observed in a population. Genomic variations in a population can arise due to single nucleotide changes in the DNA or structural changes to chromosomes.

Copy number variation or CNV is an umbrella term that defines the structural variations involving DNA segments of more than 1 kilo base pair.

If the chromosomal segment involved contains a gene, the CNVs can increase the copy number of that gene by duplication and insertion or decrease it by deletion that results in null genotype.

Therefore, some individuals may have two or even more copies of a gene, or no copies at all. For example, some people of European genetic ancestry may carry two copies of the Rhesus blood group gene, RHD, while some may have just one and others none at all.  

CNV can affect the phenotypes that are dependent on the number of functional gene copies. In European-American and Asian regions where starch-based diets are common, the population shows a higher copy number of gene AMY1, a gene which is involved in starch metabolism.

CNVs are also linked with several diseases such as psoriasis, Parkinson’s and behavioral disorders like autism and Schizophrenia.

While CNVs usually cover large DNA sequence variations, single nucleotide polymorphisms or SNPs are random, single base substitutions found throughout the genome.

Such base substitutions occur once every 1000 nucleotides; however, not all of them qualify as SNPs. Generally, only a nucleotide variation that is found in more than 1% of the population is referred to as SNP.

SNPs can confer various diseases such as diabetes or cancer. For example, in patients with sickle cell anemia, a single base substitution from adenine to thymine in a specific locus of the beta-globin gene causes sickle-shaped red blood cells.