Table I. Four SGK1 mutations found in 285 glioblastomas sequenced, 4 tumors with one mutation each. Amino acid example: p.F241F (Reference (unmutated) C, alt (mutation) T, Substitution - coding silent, position 241, F→F; F or phe: symbol for phenylalanine). A missense mutation is a form of point mutation resulting in a codon that codes for a different amino acid, and thus causes the synthesis of a protein with an altered amino acid sequence during translation. A frameshift deletion mutation (Frame_Shift_Del) is a genetic mutation caused by deletion of a number of nucleotides in a DNA sequence that is not divisible by three. Due to the triplet nature of gene expression by codons, the deletion can change the reading frame (the grouping of the codons), resulting in a completely different translation from the original.