different mutation types

Many different mutation types can result in loss of function
of the gene product and when a variety of mutations in a gene
cause a single phenotype, these are all likely to represent loss of
function mutations. In fragile X syndrome, for example, the
most common mutation is a pathological expansion of a CGG
trinucleotide repeat that silences the FMR1 gene. Occasionally
the syndrome is due to a point mutation in the FMR1 gene, also
associated with lack of the gene product that produces the
same phenotype.