What are some examples of loss of function mutations?
There are many examples for loss of function due to mutations.
They can be a basic as the inability to make insulin which causes diabetes, Type I.
Another is sickle cell anemia. In people with sickle cell anemia, the sequence of amino acids in hemoglobin is slightly different, and so it doesn't carry oxygen as it should.
A more complex mutation is seen in PKU or Phenylketonuria. It is common enough that newborns are tested at birth. Children who are not screened and treated, seem normal at birth but begin to show abnormal milestone developments, an undeveloped brain and severe learning disabilities.