Office Assistant Tasks. 1  Answer phones, direct calls and take messages. 2  Operate office machines; photocopiers and scanners, facsimile machines, voice mail systems and personal computers. 3  Maintain and update filing, inventory, mailing and database systems. 4  Open, sort and route incoming mail, answer correspondence and prepare outgoing mail.
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.
However, these mistakes are rare, and the cell has repair mechanisms that can repair some damage. - Sometimes a permanent change occurs in a cell's DNA and this is called a mutation. - Because a mutation in a gene causes a change in the protein that is made, the enzyme is nonfunctional. Types of mutations - Mutations can range from changes in a single base pair in the coding sequence of DNA to the deletions of large pieces of chromosomes. - Point mutations involve a chemical change in just one base pair and can be enough to cause a genetic disorder. - A point mutation in which one base is exchanged for another is called a substitution. - Most substitutions are missense mutations, where the DNA code is altered so that it codes for the wrong amino acid. - Other substitutions, called nonsense mutations, change the codon for an amino acid to a stop codon. Nonsense mutations cause translation to terminate early. Nearly all nonsense mutations lead to proteins that cannot function normally. - Another type of mutation that can occur involves the gain or loss of a nucleotide in the DNA sequence.