Protein production by the ribosome ultimately depends on the triplet sequence of DNA. Each triplet codes for one amino acid, thus, alterations in this triplet code will change the amino acid if it codes for a different amino acid and is not degenerate i.e. has multiple codons. The outcome may be nothing (if the code is degenerate, producing the same amino acid), the synthesis of a wrong amino acid which alters primary (and hence tertiary) structure of the protein, or if it produces a stop codon (thereby, the protein is truncated and is no longer functional in most scenarios)
In addition to single base changes, indels (insertions or deletions) can have greater effects upon protein sequence through base-shifting the downstream base sequence by 1, changing the primary sequence downstream. Other large scale changes include chromosome translocation - reciprocal or unbalanced translocation can occur in the middle of a gene, resulting in a different base sequence upstream of the translocation and hence, coding for a different primary sequence of the protein.