Biotechnology test

Polymerase Chain Reaction

Three steps cycle: heating, cooling, replication

Targeted strand is only heated after the third cycle.

Gel Electrophoresis

digested DNA molecules are injected to the wells

they travel from the negative electrode to the positive electrode

their rate of movement depends on their sizes, with the smaller fragments travelling further and larger DNA fragments nearer to the negative electrode

Restriction Fragment Length Polymorphism

As the amount of DNA is too large and the difference between their sizes are similar, it appear as smear, RFLP is then needed

The next step is Southern blotting to attract the DNA to travel from the gel to the nylon membrane

The nylon membrane is then put in a plastic bag with radioactive probe inside

placed against X-ray film---autoradiography

Vector Cloning

isolate plasmid DNA and select the DNA with the desired gene

insert the desired gene into the plasmid

use the same restriction enzyme to cut the DNAs

DNA ligase is used to fuse them together permanently

put the recombinant plasmid back into the bacteria

clone the bacteria and select bacterias with the desired gene