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The use of polymorphic DNA and protein markers for the third complement component for determining linkage of familial
Insights
Researchers studied familial hypercholesterolaemia (FH) and the C3 gene using DNA and protein markers. While linked, C3 is not close enough on chromosome 19 to be a reliable diagnostic marker for FH.
Area of Science:
- Genetics
- Molecular Biology
- Biochemistry
Background:
- Familial hypercholesterolaemia (FH) is a genetic disorder causing high cholesterol.
- The third complement component (C3) gene has been previously suggested to be linked to FH.
Purpose of the Study:
- To assess DNA markers for FH diagnosis and study.
- To confirm the linkage between FH and the C3 gene.
Main Methods:
- Analysis of DNA and protein polymorphisms of the C3 gene.
- Studied inheritance patterns in 10 families with FH.
- Combined new data with previously published results.
Main Results:
- Confirmed loose linkage between the C3 gene and the FH gene (lod score max 2.0, recombination distance 0.15).
- Combined data yielded an overall lod score max of 4.75 at a recombination distance of 0.2.
- Genes are inherited together in approximately 80% of children.
Conclusions:
- The FH gene is located on chromosome 19, linked to C3.
- C3 is not sufficiently close to the FH gene for use as a diagnostic marker.
Abstract:
We have used DNA and protein polymorphisms for the third complement component (C3) to assess the potential of DNA markers in the diagnosis and study of familial hypercholesterolaemia (FH), and to confirm the reported linkage between FH and C3. The inheritance of FH and the C3 gene has been studied in 10 families by combining information from both the protein and DNA polymorphisms. Our results confirm that the C3 gene is loosely linked to the gene causing FH (lod score maximum of 2.0) at a recombination distance of 0.15. When these results are combined with previously published data the overall lod score maximum is 4.75 at a recombination distance of 0.2, meaning that the two genes will be inherited together in only about 80% of children. These results confirm that the gene that causes familial hypercholesterolaemia is linked to C3 and is therefore on chromosome 19, but C3 is not close enough to be used as a diagnostic marker.