Techniques in Biotech - Recombinant DNA

What is Recombinant DNA also known as?

Genetic engineering

What is Recombinant DNA?

Process of splicing DNA from one organism into another organism 

What are the uses of Recombinant DNA?

Variety of uses 

• Synthetic hormone production 

• Transgenic organisms – e.g. wheat that is resistant to herbicides 

• Gene therapy for diseases 

What is DNA?

DNA Review  

• The sequence of bases that make up the DNA code for protein production by the cell 

 

• A gene is a series of bases that code for the production of a particular protein 

Describe the process of Recombinant DNA

1. Isolating (cutting out) the insulin gene from a healthy human cell, using a restriction enzyme 

 

2. Treating a piece of bacterial DNA with the same restriction enzyme 

 

3. Splicing the human insulin gene into the bacterial DNA 

 

4. Sticking the spliced pieces together with the enzyme DNA Ligase 

 

5. Putting the bacterial DNA back into the bacterium 

What are restriction enzymes?

Restriction enzymes are enzymes that cut DNA when they encounter specific base sequences 

What are the properties of restriction enzymes

• There are different types of restriction enzymes that target different base sequences 

• Some make staggered cuts with sticky ends 

  • They target specific base sequences (recognition sites) that are palindromic (they read the same backwards and forwards) 

  • The restriction enzyme cuts along the recognition site, producing a staggered cut with sticky ends. Other base sequences can bind if they have the same staggered cut and sticky ends. 

What is DNA Ligase?

• An enzyme that sticks two DNA sequences together

Once two DNA sequences are put together with the same staggered cuts and sticky ends, they are treated with an called DNA Ligase which sticks them together 

What base sequences can match?

• Any if they have been treated with the same restriction enzyme

Two pieces of DNA that have been treated with the same restriction enzyme will have the same staggered cut and sticky ends – they will match even if they are from different types of organism. 

Splicing human genes into bacteria 

• Bacteria have long strands of DNA, but also have smaller, circular strands of DNA in their cytoplasm 

 

• These small, circular strands of DNA are called plasmids 

 

• Plasmids are removed from bacteria with the same restriction enzyme used to isolate human genes, so the human gene can be spliced into the plasmid 

 

• The plasmid (now containing a human gene, e,g. For insulin) is a vector (carrier) that transports the human gene 

 

• The plasmid is placed into a new bacterium, so that bacterium will carry the human gene. If it is carrying the human insulin gene. It will produce the hormone insulin.