Genes and chromosomes 4: common genetic conditions

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This article has been double-blind peer reviewed

In this article…

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An aneuploidy is a deviation from the diploid number - the most well-known is Down’s syndrome

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Trisomies are disorders in which an extra chromosome is present

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People with Klinefelter’s syndrome have an extra X chromosome, but their Y chromosome means they have a male phenotype

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Turner’s syndrome is the only survivable chromosomal disorder in which an entire chromosome is missing

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Single-gene defects can cause inheritable genetic diseases such as cystic fibrosis, albinism and Huntington’s disease

Genetic disease often leads to unviable embryos or babies with very short lifespans. However, there are also survivable genetic diseases - for example, Down's syndrome, Klinefelter's syndrome, cystic fibrosis and Huntington's disease. Genetic diseases can be broadly classified into those affecting entire chromosomes (chromosomal disorders) and those affecting single genes (single-gene defects). This article explores these diseases, explains their causes, describes their clinical features and depicts their rules of inheritance. It is the fourth and last in our series on genes and chromosomes.


Knight J, Andrade M (2018) Genes and chromosomes 4: common genetic conditions. Nursing Times; 114: 10, 54-58.

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