Definition

The XIST gene is located in the Xq13.2 region and encodes a long non-coding RNA transcribed from the X chromosome inactivation center, which initiates and maintains random inactivation of one X chromosome in females (Lyonization). A deletion in the XIST region can disrupt the X-inactivation pattern, leading to selective inactivation of structurally abnormal X chromosomes.

Method

FISH analysis

Accepted sample types

Amniotic fluid, Chorionic villus, Cord blood

Inheritance

Can show X-linked inheritance; structural abnormalities in the XIST region can be germline or de novo.

Related Tests

Inheritance Patterns

Describes how a genetic condition is passed on within a family. There are five main patterns

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Carrier (Heterozygous / Homozygous)

Why it matters: In autosomal recessive inheritance, when each parent is a carrier (while both appear healthy), the chance of their child being born with the disease is 25% in each

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VUS (Variant of Uncertain Significance)

This is the situation where the test has detected a change in the DNA, but the role of this change in the development of disease is unconfirmed.

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How to Read a Genetic Test Result (Positive / Negative / VUS)

A genetic test result falls into three main categories

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Types of Genetic Tests

A genetic test is a type of medical test that detects changes in genes, chromosomes or proteins. Today there are more than 77,000 genetic tests available.

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