Question

Genetic engineering is possible because

• A. we can cut DNA at specific sites by endonucleases like DNase I
• B. restriction endonucleases purified from bacteria can be used in vitro
• C. the phenomenon of transduction in bacteria is well understood
• D. we can see DNA by electron microscope

Answer 1

The correct option is B restriction endonucleases purified from bacteria can be used in vitro

DNA restriction endonucleases are a class of restriction endonucleases that cut double-stranded DNA molecules only at sites characterized by a specific nucleotide sequence. Restriction enzymes are isolated from bacterial cells, and are tools for molecular biologists. Several hundred restriction enzymes are now known, each with a specific sequence requirement dictating where it will cut DNA. Some, such as Hin d III, make staggered cuts leaving ‘sticky ends’ three nucleotides long protruding on one strand from each severed terminus; Sma I makes clear cuts in both strands at the same place that are known as genetic ‘blunt ends’