Genetics of Antibiotic Resistance Flashcards
What are transposons?
Sequence of DNA that can change its position within a genome, leading to mutations or reversing them, altering a cell’s genetic identity.
What are insertion sequences?
Short DNA sequences that act as a simple transposable element (TE), there is a gene which lies between two inverted repeat sections
What are integrons?
These are a special class of composite elements carrying gene cassettes
What are the differences between bacterial and eukoaryotic genes?
Bacterial genomes: 2-6,000 Kb in length, containing 2-6,000 genes with a haploid circular chromosome and often there are extrachromosomal DNA present in plasmids Eukaryotic genomes (human): 3 million Kb length, 25,000 genes with a diploid and linear 23 pairs of chromosomes.
What is bacterial cell conjugation?
Bacterial cells connect via a pilus, the pilus retracts and then forms a conjugation bridge. The plasmid is then read from a complementary strand until it is replicated in the other fused cells, and thereafter it will separate with both cells having the plasmid, and therefore the genetic data has also been transferred.
What is bacterial cell transformation?
This is where there is transfer of ‘naked’ DNA leading to this DNA being integrated into chromosomes by homologous recombination
What is bacterial cell transduction?
Transfer of genetic material through the aid of bacteriophages (viruses) which infect bacterial cells and use them as host, and during the process can integrate their own genetics into the host cell’s DNA in order to allow it to reproduce.
Outline the main ways antibiotic resistance develops
Destruction of drug, modification of drug, drug impermeability or efflux, target modification, target bypass
How may bacterial become resistant due to target modification?
Where there is a small mutation in the target receptor which continues to allow it to function but prevents the drug from being able to bind to the target to exert it’s action with affinity
How may bacterial become resistant due to drug efflux?
Bacteria may develop a mechanism whereby they can remove the antibiotic quicker than it takes for the antibiotic to act on the target, and therefore this can convey resistance to a multitude of different antibiotics
How may bacterial become resistant due to drug breakdown?
Bacteria develop a mechanism of inactivating or breaking down the antibiotic before it has the opportunity to work, for example, lactams.
How may bacterial become resistant due to drug modification?
Bacteria may acquire genes which can code for enzymes which modify aminoglycosides, and these can then be used to add small molecules to the antibiotic and prevent it from binding to its target
