Question

Due to the chloramphenicol resistance gene, one is able to select a transformed cell in the presence of chloramphenicol. The chloramphenicol resistance gene, in this case, is called:
A. Origin of replication
B. Cloning sites
C. Selectable marker
D. None of the above

Answer 1

Hint: Selectable markers are often antibiotic resistance genes. They assist in artificial selection. They help in identifying transformants and selectively permitting their growth while rejecting non-transformants in a cloning vector. An example of a selectable marker is the ampicillin resistance gene. All transformed cells contain the resistance gene and can survive in a medium containing ampicillin whereas non-transformed cells die.

Complete step-by-step solution:
Chloramphenicol is called a general inhibitor of translation in bacteria. It is a bacteriostatic agent, sometimes also with bactericidal activity, which binds to the 50S ribosomal subunit and blocks the elongation of peptides during the biosynthesis of proteins. Chloramphenicol resistance may be used as a selection marker for genetic experimentation in Chlamydia. The selectable markers are described as the gene introduced into a host cell, containing selectable markers that confer a trait appropriate for artificial selection. Selectable markers are the genes present in the cloning vectors that assist in removing the non-transformants. For example, herbicide resistance genes, antibiotic resistance genes, etc.
The origin of replication is the ability to reproduce with another plasmid in a similar bacterial cell. These plasmids cannot co-exist in the similar bacterial cell and hence they form a second plasmid of the similar compatibility group. Once the plasmids are separated in various cells, correct replication is formed.
The cloning site is the place where DNA is inserted into the vector. The restriction enzyme identifies the recognition site and cuts the DNA for the insertion of foreign DNA.

Therefore the correct answer is Option C.
Note:Selectable markers help in finding and choosing non-transformants and transformants. The selectable marker is the sequence on DNA, which helps in recognising and eliminating non-transformants and selectively enabling the growth of transformants. The vector needs a selectable marker for this purpose.