Principles and tools of genetic technology
Genetic engineering
- Recombinant DNA is DNA joined from two different sources.
- Genetic engineering deliberately changes an organism's genes — often by transferring a gene so it is expressed.
- It uses a clever toolkit of enzymes and carriers.
Practice
Recombinant DNA is:
Recombinant DNA combines DNA from two sources — e.g. a human gene joined into a bacterial plasmid.
Getting the gene
The gene to transfer can be obtained by:
- cutting it out of a donor's DNA,
- making it from mRNA using reverse transcriptase,
- building it chemically from nucleotides.
Practice
Reverse transcriptase is used to:
Reverse transcriptase builds a DNA copy from mRNA — one way of obtaining the gene to transfer.
The tools
| Tool | Role |
|---|---|
| restriction endonuclease | cuts DNA at a specific sequence, leaving sticky ends |
| DNA ligase | joins DNA pieces together |
| plasmid | a DNA ring used as a vector to carry the gene into a cell |
| reverse transcriptase | makes DNA from an mRNA template |
- A promoter (the "switch") must go in too, or the gene stays silent.
- A marker gene (e.g. one that glows) shows the transfer worked.
Practice
Which tool cuts DNA, leaving "sticky ends"?
Restriction enzymes cut at specific sequences leaving sticky ends; ligase then joins matching ends.
Practice
A plasmid is used in genetic engineering as a:
The plasmid is a cloning vector: the gene is joined into it and the recombinant plasmid is taken up by a cell.
Practice
A marker gene helps scientists by:
A marker gene (e.g. coding for a fluorescent product) shows which cells took up the new gene.
Gene editing
- Gene editing is a precise form of genetic engineering.
- It inserts, deletes or replaces DNA at an exact site in the genome.
You've got it
Key idea
- recombinant DNA = DNA joined from two sources; genetic engineering transfers a gene to be expressed
- get the gene by cutting it out, reverse transcriptase (from mRNA), or synthesis
- tools: restriction enzyme (sticky ends), ligase (join), plasmid vector, plus a promoter + marker gene
- gene editing = precise insert/delete/replace at an exact site