Karyotype

A karyotype is a test that evaluates the number and structure of an individual's chromosomes in order to detect abnormalities. This chromosomal profile provides valuable information that can aid in the diagnosis of genetic diseases and syndromes.<ref>,

 Exclusion of chromosomal mosaicism: tables of 90%, 95% and 99% confidence limits and comments on use, 
 American Journal of Human Genetics, 
 1977,
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Karyotype of a human male, showing 22 pairs of autosomes and one pair of sex chromosomes (XY)

Procedure

To perform a karyotype, cells (typically white blood cells) are cultured and arrested during metaphase, the phase of cell division when chromosomes are most visible. The cells are then stained and photographed under a microscope. The resulting image allows the identification and arrangement of chromosomes based on their size, the position of the centromere, and the pattern of bands produced by the staining.<ref>,

 The Developing Human: Clinically Oriented Embryology, 
 Elsevier, 
 2016,</ref>

Types of Karyotype Analysis

There are different types of karyotype analysis including the standard karyotype, high-resolution karyotype, and spectral karyotyping (SKY). While standard karyotyping is sufficient for detecting large chromosomal abnormalities such as trisomies or large deletions, high-resolution karyotyping and SKY allow for the detection of more subtle abnormalities such as translocations or inversions.<ref>,

 Multicolor spectral karyotyping of human chromosomes, 
 Science, 
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 Vol. 273(Issue: 5274),
 pp. 494–497,
 DOI: 10.1126/science.273.5274.494,
 PMID: 8662537,</ref>

Clinical Applications and Interpretation

Karyotyping is used in prenatal diagnosis to detect chromosomal abnormalities such as Down syndrome (trisomy 21), Edward syndrome (trisomy 18), and Patau syndrome (trisomy 13). It is also employed in the diagnosis of sex chromosome abnormalities such as Turner syndrome and Klinefelter syndrome. In cancer diagnosis and research, karyotyping can help identify chromosomal translocations that may be driving the disease.<ref>,

 Karyotype-phenotype correlations in gonadal dysgenesis and their bearing on the pathogenesis of malformations, 
 Journal of Medical Genetics, 
 1965,
 Vol. 2(Issue: 2),
 pp. 142–155,
 DOI: 10.1136/jmg.2.2.142,
 PMID: 14290416,</ref>

Limitations and Future Directions

While karyotyping is a valuable tool for detecting large chromosomal abnormalities, it is not sensitive enough to detect smaller changes such as microdeletions or duplications. With the advent of technologies like microarray analysis and next-generation sequencing, it is now possible to identify these smaller genetic changes. However, karyotyping remains an important tool in the diagnostic arsenal for genetic disorders.<ref>,

 Consensus statement: chromosomal microarray is a first-tier clinical diagnostic test for individuals with developmental disabilities or congenital anomalies, 
 American Journal of Human Genetics, 
 2010,
 Vol. 86(Issue: 5),
 pp. 749–764,
 DOI: 10.1016/j.ajhg.2010.04.006,
 PMID: 20466091,</ref>

See Also

• Chromosome
• Down syndrome
• Klinefelter syndrome
• Turner syndrome
• Cytogenetics

References

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