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Karyotyping

Karyotyping

Karyotyping

Karyotyping

Sex-linked Disorders

Sex-linked Disorders

Like autosomes, sex chromosomes contain a variety of genes necessary for normal body function. When a mutation in one of these genes results in biological deficits, the disorder is considered sex-linked.

Nondisjunction

Nondisjunction

During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed sister chromatid separation during meiosis II. In some species, notably plants, nondisjunction can result in an organism with an entire additional set of chromosomes, which is called polyploidy. In humans, nondisjunction can occur during male or female gametogenesis and the resulting gametes possess one too many or one too few chromosomes.

Nondisjunction

Nondisjunction

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate correctly and move to the opposite poles of the cells. This produces daughter cells with abnormal chromosome numbers. Nondisjunction is common during anaphase I or anaphase II of meiosis. Mutations in synaptonemal complex proteins that attach homologous chromosomes increase the chances of nondisjunction in anaphase I of meiosis I. In contrast, mutations in topoisomerases and condensins that hold sister...

Sex Linked Disorders

Sex Linked Disorders

Like autosomes, sex chromosomes contain a variety of genes necessary for normal body function. When a mutation in one of these genes results in biological deficits, the disorder is considered sex-linked.

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Array Comparative Genomic Hybridization (Array CGH) for Detection of Genomic Copy Number Variants

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Published on: February 21, 2015

18q deletion syndrome - A case report.

Magdalena Budisteanu¹, Aurora Arghir, Sorina Mihaela Chirieac

¹"Prof. dr. Alexandru Obregia" Clinical Hospital of Psychiatry, Bucharest, Romania.

|October 7, 2011

Summary

A deletion on chromosome 18q (18q21-qter) in a young boy caused severe developmental delays, hypotonia, deafness, and dysmyelination. Growth hormone therapy was ineffective and discontinued due to adverse effects.

Keywords:

18q deletion GH therapy hypotonia

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Area of Science:

Genetics
Neurology
Pediatrics

Background:

Chromosome 18 deletions are rare genetic disorders associated with various developmental abnormalities.
Distal deletions of 18q can lead to a spectrum of clinical manifestations, including intellectual disability and neurological deficits.

Observation:

A 3-year-old boy presented with severe mental retardation, hypotonia, deafness, cerebral dysmyelination, low immunoglobulin A levels, and dysmorphic features.
Karyotype analysis and Fluorescence In Situ Hybridization (FISH) confirmed a distal deletion of chromosome 18q (18q21-qter).

Findings:

The patient exhibited a complex phenotype consistent with distal 18q deletion syndrome.
No cryptic rearrangements involving other chromosomes were detected.
Growth hormone therapy did not yield clinical improvement and was discontinued due to an unexplained febrile episode and patient regression.

Implications:

This case highlights the significant impact of distal 18q deletions on neurodevelopment and immune function.
Further research is needed to understand the specific genes within the 18q21-qter region responsible for these phenotypes.
The findings underscore the importance of genetic diagnosis in patients with unexplained developmental and neurological disorders.