Copy-number variants are defined as sections of DNA that exist in a variable copy number when comparing it to the reference genome and are larger than 1 kb in size. This definition is broad and includes deletions, duplications, and large copy number variants. If the copy number variant is present in 1% or more of the population then it is also considered a copy-number polymorphism. There was a study on the global variation in copy number in the human genome which questioned the characteristics of copy number variants in the human genome. It was known that copy number variation in the human genome is important but at this point of time, it had not yet been fully understood. Human genome variation itself is very diverse as there are many types including inversions, duplication, SNPs, and other forms. They surveyed the genomes of 270 individuals, from a variety of populations, for copy number variants with technologies such as SNP arrays. Their results showed that many copy number variants had specific arrangements of linkage disequilibrium which revealed the copy number variation in all of the different populations. The study concluded that twelve percent of the genome contained CNVRs. They were found to be involved in more of the DNA in each genome than single nucleotide polymorphisms. This was a remarkable discovery since single nucleotide polymorphisms have been known to be the greatest in number in the human genome. In terms of size, however, these type of structural variants were found to have a larger presence in the human genome.
