Turner syndrome is caused by the absence of a complete or partial X chromosome in females. This chromosomal abnormality occurs randomly, usually during the formation of the egg or sperm cell.
Here's a more detailed breakdown:
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Chromosomal Abnormality: Females typically have two X chromosomes (XX). In Turner syndrome, one X chromosome is either missing entirely or structurally altered.
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Random Occurrence: The error leading to the missing or altered chromosome usually happens by chance during the formation of the egg or sperm in one of the parents, or early in fetal development.
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Types of Chromosomal Abnormalities in Turner Syndrome:
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Monosomy X (45,X): This is the most common type, where one X chromosome is completely missing in all cells.
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Mosaicism: Some cells have the typical XX chromosomes, while others have a missing or altered X chromosome. This can lead to varying degrees of symptoms.
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X Chromosome Abnormalities: Part of one X chromosome is missing or rearranged. A common example is a ring chromosome, where the ends of the X chromosome fuse together to form a ring.
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Y Chromosome Material: In some rare cases, some cells may contain both a missing or altered X chromosome and some Y chromosome material. This requires careful monitoring due to a slightly increased risk of certain cancers.
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Not Inherited: Turner syndrome is generally not inherited. It's a spontaneous genetic event. However, recurrence in the same family, while rare, can occur. Genetic counseling is recommended for concerned families.
Because the X chromosome carries many genes essential for development, the absence or alteration of one X chromosome can cause the various physical features and health problems associated with Turner syndrome. These can include short stature, ovarian insufficiency (leading to infertility), heart defects, and certain learning difficulties.
