The X chromosome is far more complex than the Y, male specific chromosome. Fragile X syndrome is a condition which is attributed to the X chromosome. Whilst the Y chromosome only carries a few hundred genes, the X chromosome carries thousands. The Y chromosome only encodes the characteristics of maleness.

Like Y chromosome testing can be used to establish biological relationships between males, the X chromosome test is used to determine biological relationships between females.

Diseases resulting from abnormalities in the X Chromosome

Fragile X syndrome, a condition which affects more males than females, develops as a result of changes on the X chromosome. It is considered to be the most common form of inherited disabilities.

This X chromosome abnormality means that the brain is deprived from the protein needed to enable it to develop properly because the protein in non synthesised by the responsible gene on the X chromosome. The symptoms of fragile X syndrome include a large body size and delays in the acquisition of language skills. It is one of the principal genes that is known to be linked to autism.

Fragile X syndrome is also referred to as:

Fragile X syndrome (FXS),

Martin Bell syndrome

Escalante’s syndrome

X chromosome Test

The X chromosome test is the ideal test if you are two or more females who wish to know if you have the same dad. X chromosomes in males are inherited from their mother whilst and X chromosome in females are inherited from both their mother and their father. The test gives a very accurate result.

The X test, as the X chromosome test is sometimes called, is what you can opt for in order to establish paternity. Yes, ideally, the first choice to consider is a paternity DNA test but in some cases the alleged father might not be available and in this case, it would not be possible to get his DNA sample. A range of relationship DNA tests are available to help solve just about any questions about familial relationships- the X chromosome test is one of them.

Conditions for an X chromosome test

  • If female siblings have the same biological mother and want to know if they have the same father they can do and X chromosome test – however, in this case, the mother’s sample is essential and the test cannot be done without it.
  • If the females involved have different mothers then it is possible to go ahead with the test even without the mother’s sample.

X Chromosome test results

This test is extremely accurate- a positive and conclusive result means a complete match between the X chromosome profiles of the females involved. In some instances genetic mutations can mean 1 or 2 genetic markers will be mismatched between the genetic profiles; in cases of just 1-2 markers, the result will be inconclusive- it is not possible to say that the females share the same dad but neither to exclude the possibility.

3 or more mismatched markers are a clear exclusion. We can conclude by saying that the X chromosome test is highly accurate and reliable. Genetic mutations on the X chromosome are rare.


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