Mutations are random because the specific changes that occur in DNA are not determined by any predictable patterns. Mutations can be caused by a variety of factors, such as environmental toxins, errors during DNA replication, and exposure to radiation. However, the exact sequence of nucleotides that will be affected by a mutation is not determined by any known factors, and therefore can be considered to be random.

It is important to note that while mutations are random at the level of individual nucleotides, they are not necessarily random at the level of the organism. For example, some mutations may be more likely to occur in certain regions of the genome, or in certain types of cells. However, the specific mutations that occur in a particular individual are still considered to be random.