Gene mutations are

A) always deleterious.
B) always beneficial.
C) radiation-induced changes only.
D) alterations in the normal sequence of bases within a gene.
E) alterations to cell cycle.

Gene mutations are alterations in the normal sequence of bases within a gene. They can be caused by various factors such as mistakes during DNA replication or exposure to mutagens (e.g. radiation). Gene mutations can have different effects on the organism, ranging from no noticeable effect to deleterious or beneficial effects. Therefore, gene mutations are not always deleterious or beneficial.