Question

Read the passage and answer the following question.

Shigella is a bacterium that is very closely related to E. coli but is incapable of fermenting lactose (lactose negative). A gene for resistance to the antibiotic ampicillin (amR) was inserted in between two of the structural genes of the lac operon and then inserted into Shigella.

Which of the following enzyme is vital for the successful completion of genetic engineering?

• A. DNA polymerase
• B. Reverse transcriptase
• C. Taq polymerase
• D. $\beta$-galactosidase
• E. Restriction endonuclease

Answer 1

Answer: (E)

Restriction endonuclease

Genetic engineering includes techniques for creation recombinant DNA which carries DNA from two different sources. Restriction endonucleases recognize specific sequences in the DNA and cut the DNA into fragments. Each restriction endonuclease has a specific restriction site; cuts at specific sites produces uniform DNA fragments with sticky or blunts ends that are easily ligated with other DNA strands; a requisite for creating rDNA. DNA polymerase and Taq polymerase are the enzymes of DNA replication while reverse transcriptase forms cDNA copy of RNA. Beta-galactosidase is an enzyme of lac operon and converts lactose into glucose and galactose. Thus, the correct answer is option E.