Biology Behind the Disease
Certain conditions, such as dwarfism, are genetic disorders. Dwarfism occurrences usually result from a random genetic mutation from either of the parents sperm or egg and not the entire genetic make-up of just one parent. About 80% of people with achondroplasia were born to normal size parents. The child can then also pass on a mutated gene or a normal gene.
Achondroplasia happens when the FGFR3 gene receptors are turned off, or aren't working properly, the cartilage fails to turn into bone and the limbs get shortened.
Achondroplasia happens when the FGFR3 gene receptors are turned off, or aren't working properly, the cartilage fails to turn into bone and the limbs get shortened.
Genes and Chromosomes
The achondroplasia disorder is located on chromosome 4, specifically on the FGFR3 gene (fibroblast growth factor receptor) which codes for a protein that maintains brain tissues and bones. In most cases achondroplasia is not inherited. However, when it is inherited, it is an autosomal dominant inheritance. The 80% of people with normal parents have received a newly mutated FGFR3 gene. The other cases have received an already mutated gene from either one or both parents. Having a homologous trait for achondroplasia is extremely fatal. Testing for the mutation in the FGFR3 gene can be done in clinical laboratories.
The picture above is of a normal female karyotype. A karyotype of someone with achondroplasia will be similar to that of someone without achondroplasia because the mutation is too small for the eye to see on a karyotype.