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Test ID: UNIPD Uniparental Disomy, Varies

Reporting Name

Uniparental Disomy

Useful For

Evaluation of patients presenting with mosaicism, confined placental mosaicism, or Robertsonian translocations


Evaluation of patients presenting with features of disorders known to be associated with uniparental disomy (eg, Russell-Silver syndrome)


Evaluation of disease mechanism in individuals with rare autosomal recessive disease and only one carrier parent

Clinical Information

Uniparental disomy (UPD) occurs when a child inherits 2 copies of a chromosome from 1 parent and no copies of that chromosome from the other parent. This error in division occurs during the formation of egg or sperm cells (meiosis). When an error causing UPD occurs during meiosis I both chromosome homologs from a single parent are transmitted, and heterodisomy results. When the error causing UPD occurs during meiosis II or as a postzygotic event, and a single parental homolog is transmitted to offspring in duplicate, isodisomy results. Meiotic recombination events within the context of UPD often result in a mixture of heterodisomy and isodisomy. UPD can involve an entire chromosome or only a segment. Mosaicism for UPD also occurs in combination with either chromosomally normal or abnormal cell lines.


When UPD occurs, the imbalance of maternal versus paternal genetic information for the involved chromosome can be associated with clinical symptoms in the affected child. However, UPD does not always impart an abnormal clinical phenotype. In fact, while isodisomy can result in disease due to a recessive allele at any location, heterodisomy is not expected to result in an abnormal clinical phenotype unless the involved chromosome or chromosomal segment includes imprinted genes. Imprinted genes demonstrate differential expression depending on parent of origin. Disorders that result from UPD of imprinted genes are not due to a defect in the imprinting mechanism itself, but rather they are due to an unbalanced parental contribution of normally imprinted alleles that results in altered expression of imprinted genes. For example, when maternal UPD 15 occurs (2 copies of the maternal chromosome 15 instead of 1 maternal and 1 paternal copy of chromosome 15), it causes Prader-Willi syndrome due to the lack of paternally expressed genes at the imprinted site.


UPD has been described for many but not all chromosomes. In addition to the rare cases of autosomal recessive disease that result from isodisomy, clinical syndromes associated with UPD have been described for only a few chromosomes, including Russell-Silver syndrome (UPD 7), Prader-Willi syndrome (UPD 15), Angelman syndrome (UPD 15), transient neonatal diabetes (UPD 6), and UPD of chromosome14.


UPD cannot be identified by gross cytogenetic analysis and requires DNA-based analysis using multiple polymorphic markers spanning the chromosome of interest. Specimens from both parents and the child or fetus are required.


An interpretative report will be provided.

Testing Algorithm

Polymerase chain reaction and microsatellite markers on the chromosome of interest are used to test DNA from the parents and the child for the presence of uniparental disomy. Uniparental disomy testing is available for all chromosomes, with the exception of chromosome 11 for certain indications. Contact the laboratory for additional information.


For prenatal specimens only: If amniotic fluid (nonconfluent cultured cells) is received, amniotic fluid culture/genetic test will be added and charged separately. If chorionic villus specimen (nonconfluent cultured cells) is received, fibroblast culture for genetic test will be added and charged separately.


See Prader-Willi and Angelman Syndromes: Laboratory Approach to Diagnosis algorithm in Special Instructions.

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
CULFB Fibroblast Culture for Genetic Test Yes No
CULAF Amniotic Fluid Culture/Genetic Test Yes No

Report Available

5 to 21 days

Day(s) Performed

Monday and Wednesday

Clinical Reference

1. Schaffer LG, Agan N, Goldberg JD, Ledbetter DH, Longshore JW, Cassidy DB: American College of Medical Genetics statement on diagnostic testing for uniparental disomy. Genet Med. 2001;3:206-211. doi: 10.1097/00125817-200105000-00011

2. Kotzot D, Utermann G: Uniparental Disomy (UPD) other than 15: phenotypes and bibliography updated. Am J Med Genet. 2005;136A:287-305. doi: 10.1002/ajmg.a.30483

3. Kotzot D: Prenatal testing for uniparental disomy: indications and clinical relevance. Ultrasound Obstet Gynecol. 2008:31:100-105. doi: 10.1002/uog.5133

4. Engel E: A fascination with chromosome rescue in uniparental disomy: Mendelian recessive outlaws and imprinting copyrights infringements. Eur J Hum Genet. 2006 Nov;14(11):1158-1169. doi: 10.1038/sj.ejhg.5201619

Method Name

Polymerase Chain Reaction (PCR)/Microsatellite markers

Specimen Type


Shipping Instructions

Specimen preferred to arrive within 96 hours of collection.

Specimen Required

For optimal interpretation of results, 3 specimens are required to perform this test. In addition to child or fetal specimen, a blood specimen from both parents is required. Each specimen must have a separate order for Uniparental Disomy (this test). Only the proband specimen will be charged. 


Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. Call 800-533-1710 for instructions for testing patients who have received a bone marrow transplant.


Submit only 1 of the following specimens:


Specimen Type: Whole blood

Preferred: Lavender top (EDTA) or yellow top (ACD)

Acceptable: Any anticoagulant

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.

Specimen Stability Information: Ambient (preferred)/Refrigerated


Prenatal Specimens

Due to the complexity of prenatal testing, consultation with the laboratory is required for all prenatal testing.



Specimen Type: Amniotic fluid

Container/Tube: Amniotic fluid container

Specimen Volume: 20 mL

Specimen Stability Information: Refrigerated (preferred)/Ambient


Specimen Type: Chorionic villi

Container/Tube: 15-mL tube containing 15 mL of transport media

Specimen Volume: 20 mg

Specimen Stability Information: Refrigerated



Specimen Type: Confluent cultured cells

Container/Tube: T-25 flask

Specimen Volume: 2 Flasks

Collection Instructions: Submit confluent cultured cells from another laboratory.

Specimen Stability Information: Ambient (preferred)/Refrigerated

Specimen Minimum Volume

Blood: 0.5 mL
Amniotic Fluid: 10 mL
Chorionic Villi: 5 mg

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Varies

Reference Values

An interpretive report will be provided.

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
UNIPD Uniparental Disomy 36917-3


Result ID Test Result Name Result LOINC Value
53356 Result Summary 50397-9
53357 Result 36917-3
53358 Interpretation 69047-9
53359 Reason for Referral 42349-1
53360 Specimen 31208-2
53361 Source 31208-2
53362 Method 85069-3
53363 Released By 18771-6


1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Molecular Genetics: Uniparental Disomy Patient Information

Mayo Clinic Laboratories | Endocrinology Catalog Additional Information: