PCR: Polymerase Chain Reaction
PCR’s purpose:
Enables us to extract a tiny quantity of DNA from a single hair or drop of blood at the scene of a crime and increase the amount of it a million times or more so that it can be analysed.
Allows us to analyse the DNA from a bacterial or viral infection in order to diagnose an illness.
Makes it possible to mass-produce DNA from fossil remains, extinct for millions of years.
PCR and Covid-19 sidenote
If you’ve had a Covid test, you will have been involved in PCR. The coronavirus is made up of RNA surrounded by proteins and lipids, but PCR only detects DNA.
The first step in the testing process is to convert the RNA to DNA using reverse transcriptase, so the DNA can then be amplified. It is then read by the PCR machine and measures the amount of coronavirus genetic material in the sample, indicating if you have the virus.
False negatives can occur up to 30% of the time with different PCR tests, meaning they’re more useful for confirming the presence of an infection than giving a patient the all-clear. They can also provide false positive results, as they’re so sensitive they can potentially signal a positive result upon detecting dead, deactivated virus still present in the body of someone who has recovered from Covid-19.
BUT, Australia is behind the times. The PCR testing process takes a few days (and the obvious associated isolation until you get a negative result).
Other countries are using Lateral Flow Tests. These basically work like a pregnancy test and give you an immediate result (so people do them at home).
Side note: You may have seen how kids in the UK are faking their latflows by using fruit juices and cola to produce a positive result.
S = where you put your swab sample
T = you have covid
C = the test has worked
Gel Electrophoresis
Gel electrophoresis’ purpose:
To separate DNA fragments, based on size.
Can be used to determine paternity or criminals: DNA profiling.
DNA molecules are negatively charged, so if you apply an electrical current to a medium they are present in, they will move towards the positive electrode.