Can someone please simplify this? - Antibiotic ResistanceWatch
I am doing a piece of coursework (Drugs and Disease module, 2nd year Biomedical Science) and am having trouble getting my head around a paragraph...
I may be overthinking it but, can someone please simplify this...
"THE TRANSFER OF RESISTANCE GENES BETWEEN GENETIC ELEMENTS WITHIN THE BACTERIUM
▼ Some stretches of DNA are readily transferred (transposed) from one plasmid to another and also from plasmid to chromosome or vice versa. This is because integration of these segments of DNA, which are called transposons, into the acceptor DNA can occur independently of the normal mechanism of homologous genetic recombination. Unlike plasmids, transposons are not able to replicate independently, although some may replicate during the process of integration (Fig. 50.7), resulting in a copy in both the donor and the acceptor DNA molecules. Transposons may carry one or more resistance genes and can ‘hitch-hike’ on a plasmid to a new species of bacterium. Even if the plasmid is unable to replicate in the new host, the transposon may integrate into the new host’s chromosome or into its indigenous plasmids. This probably accounts for the widespread distribution of certain of the resistance genes on different R plasmids and among unrelated bacteria.
Gene cassettes and integrons
▼ Plasmids and transposons do not complete the tally of mechanisms that natural selection has provided to confound the hopes of the microbiologist/chemotherapist. Resistance – in fact, multidrug resistance – can also be spread by another mobile element, the gene cassette, which consists of a resistance gene attached to a small recognition site. Several cassettes may be packaged together in a multicassette array, which can, in turn, be integrated into a larger mobile DNA unit termed an integron. The integron (which may be located on a transposon) contains a gene for an enzyme, integrase (recombinase), which inserts the cassette(s) at unique sites on the integron. This system – transposon/integron/multiresistance cassette array – allows particularly rapid and efficient transfer of multidrug resistance between genetic elements both within and between bacteria."
Gene cassette: genes that are able to wrap itself into a circular form, and is also able to transfer from one bacteria to another.