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# Chromosomes and cytogenetics

Changes in chromosome number and structure, and the tests that find them.

11 pages

## Topics

- [**Chromosome abnormalities: number and structure** An extra chromosome, a missing one, or a piece lost or moved alters many genes at once and…](https://durgical.com/en/general-pathology/chromosome-abnormalities-number-and-structure/)
- [**Trisomies 21, 18 and 13, and the 22q11.2 deletion** The three trisomies that reach birth and the commonest microdeletion have features typical…](https://durgical.com/en/general-pathology/trisomies-21-18-and-13-and-the-22q11-2-deletion/)
- [**Sex chromosome disorders: Klinefelter and Turner** An extra X chromosome in a male (Klinefelter) or a missing one in a female (Turner) mainly…](https://durgical.com/en/general-pathology/sex-chromosome-disorders-klinefelter-and-turner/)
- [**Genetic tests: what each one finds** Each genetic test looks at a different scale, from whole chromosomes to single letters of DNA…](https://durgical.com/en/biochemistry/topics/genetic-tests-what-each-one-finds/)
- [**FISH (fluorescence in situ hybridization)** FISH uses fluorescent DNA probes that stick to one exact place on a chromosome, to see under the…](https://durgical.com/en/biochemistry/topics/fish/)
- [**DNA microarrays** A microarray is a chip with thousands of DNA probes that measures the expression of many genes…](https://durgical.com/en/biochemistry/topics/dna-microarrays/)
- [**22q11.2 deletion (DiGeorge): the third and fourth pouches** A small piece of chromosome 22 is missing](https://durgical.com/en/embryology/22q11-2-deletion-the-third-and-fourth-pouches/)
- [**Differences of sex development: CAH, AIS and 5α-reductase** Conditions in which chromosomes, gonads and genitalia do not follow the typical pattern](https://durgical.com/en/embryology/differences-of-sex-development-cah-ais-and-5-reductase/)

## Conditions and syndromes

- [**Down syndrome (trisomy 21)** A chromosomal condition from an extra chromosome 21, with intellectual disability, typical…](https://durgical.com/en/conditions/down-syndrome/)
- [**16p11.2 deletion syndrome** A small recurrent loss of chromosome 16 that raises the chance of speech delay, autism, obesity…](https://durgical.com/en/conditions/16p11-2-deletion-syndrome/)
- [**Miller–Dieker syndrome (lissencephaly)** A deletion on chromosome 17 that stops neurons from migrating in the fetal brain, leaving a…](https://durgical.com/en/conditions/miller-dieker-syndrome/)

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This section is an index: it gathers pages from Biochemistry, Pathology, Embryology and other sections without repeating them. Educational content; it does not replace a geneticist's assessment or genetic counselling.

Representative model, for educational purposes only.

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Source: https://durgical.com/en/genetics/chromosomes/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/genetics/chromosomes/