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Can a change in the number of genes affect health and development?
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Mutationsanddisorders

Can a change in the number of genes affect health and development?

Copy number variations (CNV) occur when individuals have an atypical number of gene copies, which can influence protein function and disease risk.

What is Copy Number Variation?

While most people inherit two copies of every gene—one from each parent—copy number variations (CNV) occur when a person has one, three, or more copies of a particular gene. In some cases, both copies may be missing. These variations result from the insertion, deletion, or duplication of large DNA segments, typically at least one thousand nucleotides (1 kilobase) in length.

Impact on Health

Because these DNA segments are often large enough to contain whole genes, CNVs can significantly influence gene activity and the functioning of the proteins they produce. Key points regarding CNVs include:

  • Prevalence: More than 10 percent of the human genome appears to contain differences in gene copy number, accounting for a significant amount of genetic diversity between individuals.
  • Health outcomes: While much of this variation is benign, some differences can influence a person’s risk of developing certain diseases, such as cancer, or affect how an individual responds to specific medications.

Frequently Asked Questions

Clinical laboratories use techniques such as array comparative genomic hybridization (array‑CGH), multiplex ligation-dependent probe amplification (MLPA), or next‑generation sequencing (NGS) to identify deletions or duplications of DNA segments. These tests compare a patient’s DNA to a reference genome to spot abnormal copy numbers.
First, discuss the findings with a genetic counselor or specialist to understand the specific genes affected and their clinical implications. Depending on the CNV, routine monitoring (e.g., blood tests, imaging) or preventive measures (e.g., early screening for associated conditions) may be recommended. Lifestyle modifications, such as a balanced diet and regular exercise, can also mitigate some risks. Staying informed about new research on the CNV can help you adapt your care plan over time.===
CNVs can cause a range of symptoms depending on the genes involved. Common signs include developmental delays, learning difficulties, congenital anomalies, or unusual responses to medications. If you notice persistent health issues that don’t fit typical patterns, or if a family member has a known CNV, a genetic evaluation may be warranted.
Yes. CNVs can alter the dosage of genes involved in drug metabolism, transport, or target receptors. For example, a duplication of a gene encoding a drug‑metabolizing enzyme may lead to faster clearance of a medication, reducing its effectiveness. Conversely, a deletion might increase drug sensitivity and risk of side effects. Pharmacogenomic testing can help tailor drug choice and dosing.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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