Definition

The ASS1 gene (9q34.11) encodes argininosuccinate synthetase, a urea cycle enzyme; biallelic variants reduce enzyme activity, preventing the conversion of ammonia to urea and causing hyperammonemia. The clinical picture varies with residual enzyme activity, with the acute neonatal form being the most common and most severe.

Gene/region examined

ASS1 - Exon 3, ASS1 - Exon 4, ASS1 - Exon 5, ASS1 - Exon 6, ASS1 - Exon 7, ASS1 - Exon 8, ASS1 - Exon 9, ASS1 - Exon 10 ASS1 - Exon 11, ASS1 - Exon 12, ASS1 - Exon 13, ASS1 - Exon 14, ASS1 - Exon 15, ASS1 - Exon 16

Method

Sequence analysis

Accepted sample types

EDTA blood, AF, CVS

Inheritance

Hereditary, autosomal recessive.

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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