Chromosome 5, uniparental disomy

Chromosome 5, uniparental disomy (UPD(5)) is a rare genetic condition resulting from both copies of chromosome 5 being inherited from one parent, rather than one copy from each parent. This can lead to a variety of clinical outcomes, depending on the specific genes involved and whether the disomy is maternal or paternal in origin. Uniparental disomy (UPD) can affect any of the chromosomes, but UPD(5) specifically refers to this phenomenon occurring on chromosome 5.

Causes

Uniparental disomy can occur through several mechanisms, including trisomic rescue, monosomic rescue, gamete complementation, and post-fertilization errors. In trisomic rescue, an embryo with three copies of a chromosome (trisomy) loses one copy, resulting in two copies from the same parent. Monosomic rescue involves the duplication of a single parental chromosome in an embryo initially lacking a copy from the other parent. Gamete complementation occurs when an egg or sperm with an extra chromosome fuses with a gamete missing that chromosome. Post-fertilization errors can also lead to UPD during early cell divisions.

Clinical Significance

The clinical significance of UPD(5) varies. It can be associated with various developmental and growth disorders, depending on the specific genes involved. If chromosome 5 contains imprinted genes—genes expressed only from the chromosome inherited from one parent—UPD(5) can disrupt normal gene expression patterns, leading to disease. However, the exact clinical manifestations of UPD(5) can be difficult to predict, as they depend on numerous factors, including whether the disomy is maternal or paternal and the presence of any recessive mutations on the duplicated chromosome.

Diagnosis

Diagnosis of UPD(5) typically involves genetic testing, including karyotyping to analyze chromosomes' structure and number, and molecular genetic tests such as microarray analysis or next-generation sequencing to detect UPD. These tests can identify abnormalities in chromosome number or structure and confirm the presence of two copies of chromosome 5 from one parent.

Management

Management of UPD(5) is symptomatic and supportive, focusing on the specific symptoms and conditions associated with the disorder. This may include developmental therapies, educational support, and medical management of any associated health issues. Genetic counseling is also recommended for families affected by UPD(5) to understand the condition, its implications, and the risk of recurrence in future pregnancies.

See Also

• Genetic disorder
• Chromosome abnormality
• Imprinting (genetics)
• Trisomy
• Karyotype