Copy number variation
Say it: KOP-ee NUM-bur vair-ee-AY-shun
Copy number variation is a difference between people in how many copies of a given stretch of DNA their genomes carry, due to deletions or duplications.
Also: CNV, copy number variant, copy number polymorphism
Definition
What is copy number variation?
Copy number variation (CNV) describes segments of DNA, typically from about a thousand to several million base pairs long, that are present in different numbers of copies in different people. Most of the genome comes in two copies, one from each parent, but a segment can be deleted, leaving one copy or none, or duplicated, giving three or more. Each such difference is a copy number variant. They arise from errors in DNA repair, replication or crossing-over between similar repeated sequences, and a variant may hold no genes, part of a gene or many genes.
CNVs account for a large share of the genetic differences between people, and everyone carries many. Most are harmless, but changing the number of copies of a gene can change how much of its product is made. A well-known example is the salivary amylase gene, which tends to have more copies in populations whose ancestors ate starch-rich diets.
Some CNVs cause disease. A deletion at 22q11.2 causes the disorder also known as DiGeorge syndrome, a duplication that includes the PMP22 gene causes Charcot-Marie-Tooth disease type 1A, and several recurring CNVs raise the risk of autism and schizophrenia. In cancer, extra copies of oncogenes such as HER2 drive tumor growth. CNVs too small to see on a karyotype are found by chromosomal microarray or genome sequencing.
Related
Terms that go with it
- MutationA mutation is a lasting change in an organism's DNA sequence, ranging from a single altered base to large rearrangements of chromosomes.
- Single nucleotide polymorphismA single nucleotide polymorphism (SNP) is a position in the genome where people differ by a single DNA base, the most common kind of genetic variation.
- Whole-genome sequencingWhole-genome sequencing is a laboratory method that reads nearly all of an organism's DNA, its genes and the noncoding DNA between them, in one test.
- KaryotypeA karyotype is the full set of chromosomes in a cell, or a picture of them sorted into pairs, used to check chromosome number and structure.
- OncogeneAn oncogene is a mutated or overactive form of a normal growth-promoting gene that pushes cells to divide uncontrollably and can cause cancer.
- GenomeA genome is the complete set of DNA in an organism or cell, including all of its genes and the stretches of DNA between them.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- NHGRI Talking Glossary: Copy Number Variation (CNV)
- NCI Dictionary of Genetics Terms: copy number variant
- NCBI MeSH: DNA Copy Number Variations
- MedlinePlus Genetics: 22q11.2 deletion syndrome
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