MCQ MAHE 2000 Microbiology Answer 08

The correct Answer is A



Plasmid transfer – often the transferred DNA is a plasmid (small ring of DNA)

1. The F (Fertility) plasmid has genes for making the conjugation pilus
2. Other plasmids have genes for the pilus ans something else (They are called self transmissible plasmids and they can transfer into species other than their own kind, sometimes into eukaryotic cells. Therefore, antibiotic resistance is frequently transferred from one type bacteria to another type)
3. Bacteria can survive without plasmids
4. Plasmids contain “extra” information for making toxins, resisting antibotics etc. Ex: Toxin synthesis in Clostriduim tetani (causes tetanus)
5. The gene for making the toxis is carried on a plasmid Ex: Resistance Plasmid carry genes for resistance to one or more antibiotics and/or resistance to metals, etc. very wide spread

• In the 1950s, Japanese physicians began to notice that some bacterial strains had evolved antibiotic resistance.
• Mutations may reduce the ability of the pathogen’s cell-surface proteins to transport antibiotics into the bacterial cell.
• Some of these genes code for enzymes that specifically destroy certain antibiotics, like tetracycline or ampicillin.
• The genes conferring resistance are carried by plasmids, specifically the R plasmid (R for resistance).
• When a bacterial population is exposed to an antibiotic, individuals with the R plasmid will survive and increase in the overall population.
• Because R plasmids also have genes that encode for sex pili, they can be transferred from one cell to another by conjugation.
  

Category: MAHE 2000 MCQs