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What are genomic imprinting and uniparental disomy?
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Inheritance

What are genomic imprinting and uniparental disomy?

Genomic imprinting and uniparental disomy are specific genetic factors that influence how certain conditions are inherited and expressed.

Genomic Imprinting

People usually inherit two copies of each gene—one from the egg cell and one from the sperm cell. While both copies are typically active, in some cases, only one copy is “turned on.” This phenomenon is known as genomic imprinting, where the activity of a gene depends on its origin (whether it was derived from the sperm or the egg).

During the formation of egg and sperm cells, genes are often marked through a chemical process called methylation, which attaches small molecules called methyl groups to DNA. These molecules identify the origin of the gene and control its activity. Imprinted genes tend to cluster together, notably on the short (p) arm of chromosome 11 and the long (q) arm of chromosome 15.

Uniparental Disomy

Uniparental disomy (UPD) occurs when a person receives two copies of a chromosome, or part of a chromosome, from one parent and no copies from the other. This can happen as a random event during the formation of egg or sperm cells or during early fetal development.

  • Health Impact: Often, UPD has no effect on health because most genes are not imprinted. However, if a person lacks active copies of essential imprinted genes, it can lead to delayed development, intellectual disabilities, or other health problems.
  • Associated Disorders:
    • Prader-Willi syndrome: Characterized by behavioral problems and uncontrolled eating.
    • Angelman syndrome: Causes intellectual disabilities and impaired speech.
    • Beckwith-Wiedemann syndrome: Associated with abnormalities on chromosome 11, characterized by accelerated growth and an increased risk of cancerous tumors.

Frequently Asked Questions

Genomic imprinting is when only one parental copy of a gene is active; the other is silenced by methylation. Uniparental disomy (UPD) is when both copies of a chromosome come from the same parent, potentially leaving the child with two active copies of an imprinted gene or none. This can lead to disorders like Prader‑Willi or Angelman if the missing or duplicated imprinted genes are critical for development.
Treatment is usually supportive and symptom‑based: growth hormone therapy for Prader‑Willi, dietary management for hyperphagia, speech and occupational therapy for Angelman, and monitoring for tumor risk in Beckwith‑Wiedemann. Early diagnosis allows for tailored interventions that can improve quality of life, but there is no cure that reverses the imprinting defect itself.
The clinician will order a chromosomal microarray or SNP array that can detect two copies of a chromosome from one parent. If UPD is suspected, they may also perform methylation studies to confirm abnormal imprinting patterns. A detailed family history and parental DNA samples help confirm the parent of origin.
UPD itself is a random event and is not directly linked to a parent’s disease. However, if the parent carries a mutation in an imprinted gene, the chance of a child inheriting two copies of that mutated gene (via UPD) is very low. The main risk comes from the inherited mutation, not from UPD.
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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