Uniparental Disomy
Also written as UPD.
reciprocal translocation, is more likely to occur if the length Uniparental disomy (UPD) is a relatively recently recognised
What our notes say
- reciprocal translocation, is more likely to occur if the length Uniparental disomy (UPD) is a relatively recently recognised (Devendra K. Gupta, Krishna M. Goel - Hutchison’s Paediatrics. chdhe-Jaypee Broth)
- born child with chromosomal imbalance arising from a Uniparental Disomy and Imprinting (Devendra K. Gupta, Krishna M. Goel - Hutchison’s Paediatrics. chdhe-Jaypee Broth)
Study material on Uniparental Disomy
- Devendra K. Gupta, Krishna M. Goel - Hutchison’s Paediatrics. chdhe-Jaypee Brothers (2012)
- SINGLE-GENE DISORDERS WITH ATYPICAL INHERITANCE MCQs
Practice questions on Uniparental Disomy
What is uniparental disomy?
- Deletion of one chromosome
- Translocation between chromosomes
- Inheritance of both chromosomes of a pair from one parent
- Having three copies of a chromosome
- Primarily an incidental laboratory finding
Answer: C. Uniparental disomy is the inheritance of both chromosomes of a pair from one parent. In Prader-Willi syndrome, this can occur when both copies of chromosome 15 are from the mother.
Why can Prader-Willi syndrome result from maternal uniparental disomy of chromosome 15?
- Chromosome is duplicated
- Occurs only after chronic exposure
- Maternal genes are overexpressed
- Patient lacks functional genes from nonimprinted paternal chromosome
- Maternal genes are deleted
Answer: D. Maternal uniparental disomy means the patient has both copies from the mother and lacks functional genes from the nonimprinted paternal chromosome 15, resulting in the same effect as paternal deletion.
In Prader-Willi syndrome caused by maternal uniparental disomy of chromosome 15, why are paternally expressed genes absent?
- Both chromosome 15 copies are maternal and the relevant maternal alleles are normally imprinted
- Both chromosome 15 copies are paternal and therefore silenced
- Chromosome 15 is absent from all cells
- The FMR1 gene is deleted
- All genes on chromosome 15 are normally inactive
Answer: A. In the relevant imprinted region, paternally expressed genes are normally active only from the paternal chromosome. Maternal uniparental disomy leaves two maternal copies, so those paternal-expression genes are functionally absent.