Question

The restriction enzymes are used in genetic engineering, because

• A. They can cut DNA at specific base sequence
• B. They can join different DNA fragments
• C. They can degrade harmful proteins
• D. They are nucleases that cut DNA at variable sites

Answer 1

The correct option is A They can cut DNA at specific base sequence

Genetic engineering
Techniques to alter the chemistry of genetic material (DNA and RNA), to introduce these into host organisms and thus change the phenotype of the host organism is called genetic engineering. Genetic engineering is one of the techniques used in biotechnology.

Role of restriction endonuclease
Restriction endonucleases are the enzymes which cleave the DNA by digesting phosphodiester bonds at the specific sequences within the DNA. Examples include EcoR I.

This helps in cutting the vector and the DNA of interest, so that the DNA of interest can be inserted into the vector. The two DNA molecules are then ligated to form rDNA in genetic engineering.

Variable cutting of DNA
If restriction enzymes, cut at random sites then vector DNA and DNA of interest would get fragmented making it unfit for forming rDNA.

Proteases
Harmful proteins are usually degraded by protein degrading enzymes like proteases present inside the cell.

DNA ligase
DNA ligases are enzymes that catalyse the formation of phosphodiester bonds between two DNA fragments, helping in uniting two DNA molecules.

For example, Ligase enzyme joins the DNA of interest with the vector DNA, thus helping in the formation of recombinant DNA in genetic engineering.

Final answer
(A)They can cut DNA at specific base sequence