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Chromosomal deletion syndromes result from deletion of parts of chromosomes. Depending on the location, size, and whom the deletion is inherited from, there are a few known different variations of chromosome deletions. Chromosomal deletion syndromes typically involve larger deletions that are visible using karyotyping techniques.
A chromosomal abnormality, chromosomal anomaly, chromosomal aberration, chromosomal mutation, or chromosomal disorder is a missing, extra, or irregular portion of chromosomal DNA. [ 1 ] [ 2 ] These can occur in the form of numerical abnormalities, where there is an atypical number of chromosomes, or as structural abnormalities, where one or ...
Disorder Chromosome or gene Type Reference Prevalence 1p36 deletion syndrome: 1 D 1:7,500 1q21.1 deletion syndrome: 1q21.1 D 2q37 deletion syndrome: 2q37 D 5q deletion syndrome: 5q D 5,10-methenyltetrahydrofolate synthetase deficiency: MTHFS [2] 7p22.1 microduplication syndrome: 7p22.1 17q12 microdeletion syndrome: 17q12 [3] [4] 1:14,000-62,500
Some chromosomes have fragile spots where breaks occur, which result in the deletion of a part of the chromosome. The breaks can be induced by heat, viruses, radiation, or chemical reactions. When a chromosome breaks, if a part of it is deleted or lost, the missing piece of chromosome is referred to as a deletion or a deficiency. [2]
Three chromosomal abnormalities with ISCN nomenclature, with increasing complexity: (A) A tumour karyotype in a male with loss of the Y chromosome, (B) Prader–Willi Syndrome i.e. deletion in the 15q11-q12 region and (C) an arbitrary karyotype that involves a variety of autosomal and allosomal abnormalities. [3]
Williams syndrome is caused by the deletion of genetic material from a portion of the long (q) arm of chromosome 7. The deleted region, which is located at position 11.23 (written as 7q11.23), is designated as the Williams syndrome critical region.
1p36 deletion syndrome is a congenital genetic disorder characterized by moderate to severe intellectual disability, delayed growth, hypotonia, seizures, limited speech ability, malformations, hearing and vision impairment, and distinct facial features. The symptoms may vary, depending on the exact location of the chromosomal deletion.
Three chromosomal abnormalities with ISCN nomenclature, with increasing complexity: (A) A tumour karyotype in a male with loss of the Y chromosome, (B) Prader–Willi Syndrome i.e. deletion in the 15q11-q12 region and (C) an arbitrary karyotype that involves a variety of autosomal and allosomal abnormalities including inversions (abbreviated as ...