In a simple way, these would be the steps to follow in a genetic engineering development:

1. Choice of a DNA [?]
A DNA fragment is chosen, which for example encodes a [?] that we want to study; We already know that the DNA is in the nucleus of the cell, so we have to extract it by breaking the cell, separating the nucleus, and isolating the total DNA.
From it, the DNA fragment we are looking for is located, cutting the chromosome into large pieces using proteins called "restriction enzymes".

2. [?] the amount of DNA
These thousands of chromosome pieces (some of which will contain "our" fragment) need to be amplified, greatly enlarged, to get a sufficient number. There are several ways to do this.
• One of them is using vectors, which are DNA transfer vehicles. It takes advantage of the bacteria have DNA sequences called plasmids, in which it is easy to introduce foreign DNA; When that foreign DNA has been put into the plasmid, you just have to put the bacteria in a [?] to reproduce geometrically, and then extract the multiplied plasmids.
• Another way of doing this, without using vectors, is through the polymerase chain reaction ([?]), which in vitro uses a bacterial protein that doubles the DNA, and through many cycles, obtains in a short time an enormous amount of DNA from a small sample; This technique is widely used in forensic medicine, being very fast and requiring very small samples.

3. Location of DNA
• Now we have to [?] all DNA fragments obtained: we pass them through a sophisticated filter, with techniques called chromatography and electrophoresis.
• We must find the fragment we are looking for: by hybridization techniques.

4. DNA [?]
• Already in our desired DNA we [?] the designed modification, using the new "cut and paste" of the restriction enzymes, obtaining a recombinant DNA.
• It is introduced into the [?] cells, which from now on will be [?] cells, as its nucleus will contain its own DNA and a strange piece.

5. [?] of protein
• Not all cells will incorporate recombinant DNA: many will die in the aggressive process that induces them to accept it, others will not accept it.
• Those who have incorporated it, if all went well, will start producing the protein (also called recombinant) that encodes the recombinant gene.