Question

RECOMBINANT DNA REVIEW

1. How are genes cut into pieces, in preparation for recombinant DNA cloning?

2. What enzyme is used to securely paste a new piece of DNA into a recombinant DNA molecue? What other process is this enzyme used in?

3. How does recombinant DNA get into bacteria? Name the process and how it works.

Answer 1

1. In recombinant DNA technology , genes are cut into pieces by the use of Restriction enzymes( Restriction endonuclease). Restriction enzymes recognise a particular DNA sequence and make a staggered cuts in the double strands of DNA . Recognised sequences will have 4-8 nucleotides and The cuts will have 2-4 nucleotides in a single strand.

2. New piece of DNA is pasted in a recombinant DNA molecue by DNA ligase enzyme.Matching single stranded sticky ends or fragments are joined by DNA ligase .It catalyses the formation of a phosphodiester bond and single DNA molecules are joined to form a recombinant DNA.

This enzyme is also used in DNA replication process.It is used to join the okazaki fragments of lagging strand during replication.

3. The process of getting recombinant DNA into bacteria is called transformation.First a vector is choosen ( usually plasmid ) as a carrier into which the donor DNA are inserted by restriction enzymes and pasted by DNA ligase enzyme.

Then the recombinant DNA plasmid is introduced into bacteria by transformation .The bacteria containing recombinant DNA replicate and make multiple copies of recombinant DNA and pass it on toto the offspring .