Read the following passage and answer the questions that follow :
We know that plasmids and bacteriophages are the most commonly used vectors in biotechnology experiments. If we can link an alien piece of DNA to the plasmid DNA, the alien DNA can be multiplied equal to the copy number of the plasmid. Engineered vectors are used these days. Study the diagram of the E. coli cloning vector pBR322 and answer the questions that follow :
(b) (ii) Identify and name two selectable markers shown in the diagram.
Show Hint
The two genes G and H are the antibiotic resistance genes ampR and tetR.
Step 1: Understand selectable markers:
A selectable marker is a gene that helps to find the host cells that took up the vector. Most often it is an antibiotic resistance gene.
Step 2: Read the diagram:
Two unnamed genes are shown on the inner ring, G and H. In pBR322 these are the two antibiotic resistance genes.
Step 3: Name them:
G is ampR, the gene for ampicillin resistance. It carries the sites for PstI and PvuI on its segment.
H is tetR, the gene for tetracycline resistance.
Final Answer:
The two selectable markers are ampR (ampicillin resistance, G) and tetR (tetracycline resistance, H).
