Frameshift mutations can be very severe. The one reason why they are often so serious is because when a frameshift mutation occurs, it causes changes in many bases downstream and can affect many of the amino acids in the protein.
Basically, a framshift mutation causes changes in the genetic material, codons, and proteins, which can lead to many complications and disorders, some of which are the Tay-Sachs disease, but it can also cause a person to be more prone to certain cancers.
