Phenotype

An important example of a phenotype is that of antibiotic resistance. This animation will demonstrate how the genotype of a bacterial cell determines whether its phenotype will be survival in the presence of the antibiotic ampicillin, a drug similar to penicillin. A bacterium that contains a plasmid carrying the gene for ampicillin resistance, denoted as ampR, is shown here in cross-section. Since the gene encodes the enzyme beta-lactamase, it is also referred to as bla. The particles on the outside of the cell wall are ampicillin molecules. To survive in the presence of the antibiotic, the cell first transcribes the ampR gene into messenger RNA, or mRNA, represented by the blue wavy line. The mRNA is then translated into a special type of protein called an enzyme, which is called beta lactamase, and is shown as a green molecule. Beta lactamase goes to the periplasm of the bacterium, between the inner and outer membranes, and binds to molecules of ampicillin before they enter the cell. In order to be active and to the kill bacteria, ampicillin molecules must contain an intact chemical structure known as a beta-lactam ring. However, beta-lactamase breaks this ring, thus inactivating the antibiotic and allowing the cell to survive. Since this bacterial cell contains a gene for ampicillin resistance, its genotype is ampR and therefore its phenotype is the ability to grow in presence of ampicillin.

Question 1: The ____________ enzyme from the periplasm of a bacterium binds to the ____________ on the ampicillin molecule in order to inactive the antibiotic and allow the cell to survive.
  1. Beta lactam ring, beta lactamase
  2. Beta lactamase, beta lactam cycle
  3. Beta lactam ring, alpha lactam ring
  4. Beta lactamase, beta lactam ring


Answer 1 Answer - (d) Beta lactamase, beta lactam ring

Question 2: The beta lactamase gene is abbreviated as ____________.
  1. bet
  2. blac
  3. amp
  4. bla


Answer 2 Answer - (d) bla