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.
Chemicals and radiation can damage genes. However, most mutations occur when the cell makes errors as it copies its genes. Genes are made out of DNA, a chemical code with four different 'letters'. Each time one of your cells divides, it must copy around 6000 million letters of DNA code. Occasionally, mistakes are made, causing mutations.