Depending on the title, there may be more or fewer duties required for the position. While smaller offices may have office assistants perform the duties of secretaries or file clerks, larger offices might have their assistants stick to one duty, such as filing.
Updated August 03, 2017. DNA mutations happen when there are changes in the nucleotide sequence that makes up the strand of DNA. This can be caused by random mistakes in DNA replication or even an environmental influence like UV rays or chemicals.
Gene mutations that occur after birth. Most gene mutations occur after you're born and aren't inherited. A number of forces can cause gene mutations, such as smoking, radiation, viruses, cancer-causing chemicals (carcinogens), obesity, hormones, chronic inflammation and a lack of exercise.