Knowra Tetrasomy X Tetrasomy X Tetrasomy X is a sex chromosome aneuploidy in which a female has four X chromosomes, usually written 48,XXXX. Its effects vary widely, and some affected people have few noticeable features.
Aneuploidy : A chromosome-number abnormality in which one or more chromosomes are present in extra or missing copies. Tetrasomy X is an aneuploidy with two extra X chromosomes.
Nondisjunction : Failure of paired chromosomes or sister chromatids to separate properly during cell division. Nondisjunction is a route by which an egg or sperm can carry extra X chromosomes.
Prenatal diagnosis : Testing during pregnancy to identify genetic, chromosomal, or developmental conditions in a fetus. Prenatal chromosome testing can detect tetrasomy X before birth.
Trisomy X : A sex chromosome aneuploidy in which a female has three X chromosomes, usually written 47,XXX. It involves one extra X chromosome rather than the two extra X chromosomes in tetrasomy X.
Human sex chromosome : A chromosome involved in sex determination and related biological traits in humans; the X and Y are the human sex chromosomes. Tetrasomy X changes the number of X sex chromosomes.
Meiosis : The specialized cell division that produces eggs and sperm with half the usual chromosome number. Errors during meiosis can produce gametes with multiple X chromosomes.
Developmental delay : A significant lag in a child's acquisition of expected motor, language, cognitive, or social skills. Developmental differences are among the reasons children with tetrasomy X may be assessed.
Pentasomy X : A sex chromosome aneuploidy in which a female has five X chromosomes, usually written 49,XXXXX. It is the adjacent higher-number X-chromosome aneuploidy.
X chromosome : One of the two human sex chromosomes, carrying genes involved in many aspects of development and cell function. The four copies that define this condition are all X chromosomes.
Fertilization : The fusion of an egg and sperm to form a zygote. Combining gametes with abnormal X counts can establish a 48,XXXX chromosome complement.
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