Bacterial genomes are often under the form a of single, chromosome. bacteria can carry in addition to their own chromosome, which can be parasites or provide useful functionality to their hosts. one can for bacterial phenotypes of interest by designing the culture medium accordingly. wildtype bacteria can grow on medium, and are thus but some mutants need that medium to be supplemented; such mutants, called incorrect answer can always grow on incorrect answer medium. incorrect answer is a mechanism requiring physical contact by which dna can be transferred between bacteria. to act as donors, cells require the incorrect answer factor, which is under plasmid form in incorrect answer f+ cells and integrated in the bacterial chromosome in incorrect answer hfr cells; cells without that factor can act as recipients and are denoted as incorrect answer f-. incorrect answer is a mechanism requiring bacterial viruses, also known as incorrect answer by which dna can be transferred between bacteria. some phages can not only use the incorrect answer cycle, which destroys the host, but can also use the incorrect answer cycle, in which they stay dormant in the bacterial genome.