Skip to content

Polymerase chain reaction (PCR) and reverse-transcriptase PCR (RT-PCR)



COVID-19 resources

covid 19 resources

For all students
For nursing assistant training
Medical and surgical asepsis (for nursing assistant training)
Hand hygiene (for nursing assistant training)
Types of personal protective equipment (for nursing assistant training)
Donning and doffing personal protective equipment (for nursing assistant training)
Standard and transmission-based precautions (for nursing assistant training)
Introduction to vital signs (for nursing assistant training)
Respiratory: Measuring respiration (for nursing assistant training)
Respiratory: Pulse oximetry (for nursing assistant training)
Respiratory: Measuring peak expiratory flow rate (for nursing assistant training)
Respiratory: Oxygen therapy (for nursing assistant training)
Respiratory: Mechanical ventilation (for nursing assistant training)
Respiratory: Oropharyngeal suctioning (for nursing assistant training)
Respiratory: Tracheostomy suctioning (for nursing assistant training)
Respiratory: Incentive spirometry (for nursing assistant training)
Respiratory: Chest physiotherapy (for nursing assistant training)
Respiratory: Collecting a sputum specimen (for nursing assistant training)
Cardiovascular: Body temperature (for nursing assistant training)
Cardiovascular: Pulse (for nursing assistant training)
Cardiovascular: Blood pressure (for nursing assistant training)
Cardiovascular: Applying antiembolic stockings and sequential compression devices (for nursing assistant training)
Gastrointestinal: Collecting a stool specimen (for nursing assistant training)
Gastrointestinal: Administering an enema (for nursing assistant training)
Genitourinary: Collecting a urine specimen (for nursing assistant training)
Genitourinary: Performing urine testing (for nursing assistant training)
Genitourinary: Urinary catheters and routine indwelling catheter care (for nursing assistant training)
Genitourinary: Removing indwelling catheters (for nursing assistant training)
Genitourinary: Condom catheters (for nursing assistant training)
Integumentary: Applying dressings and bandages (for nursing assistant training)
Endocrine: Blood glucose testing (for nursing assistant training)
GI/GU: Bladder and bowel training (for nursing assistant training)
GI/GU: Routine ostomy care (for nursing assistant training)
GI/GU: Monitoring fluid intake and output (for nursing assistant training)
Repositioning clients (for nursing assistant training)
Transferring clients (for nursing assistant training)
Assisting with ambulation (for nursing assistant training)
Assistive devices for ambulation (for nursing assistant training)

Polymerase chain reaction (PCR) and reverse-transcriptase PCR (RT-PCR)


0 / 14 complete
High Yield Notes
11 pages

Polymerase chain reaction (PCR) and reverse-transcriptase PCR (RT-PCR)

14 flashcards
External References

Our DNA contains loads of information, neatly stacked to insanely small sizes, able to fit within a cell nucleus.

A single DNA molecule has two strands, which wrap one around one another to form a double helix.

Each single strand of DNA is composed of a sequence of four types of nucleotides - which are the individual letters or building blocks of DNA.

Nucleotides of DNA are made up of a sugar - deoxyribose, a phosphate, and one of the four nucleobases - adenine, cytosine, guanine, and thymine - or A, C, G, T for short.

The nucleotides on one strand form hydrogen bonds to complementary nucleotides on the other strand; specifically, A bonds with T via two hydrogen bonds, and C bonds with G, via three hydrogen bonds.

Additionally, the two DNA strands also have a “direction” - meaning, one of them runs from the 3’ end to the 5’ end, while the other one runs from the 5’ end to the 3’ end.

Kinda like two snakes coiled up together, but facing in different directions. Every single protein of our body is encoded through combinations of just four nucleotides.

When there are errors in our genetic information, diseases occur. And let’s be honest, we were always interested in knowing what was written in our DNA.

Polymerase chain reaction, or PCR for short, is a technique used in molecular biology to amplify a segment of DNA. Let’s take a step back. A single copy of DNA is not very much DNA.

So to work with DNA, we basically make lots and lots of lots of copies of it, so that it’s easier to analyze. For example, if we want to visualize it, we can use a technique called gel electrophoresis.

PCR is based on DNA replication, a process that our cells normally use to duplicate their genetic material before dividing in two identical daughter cells.

So first of all, we’re going to need a machine called a thermal cycler - that’s where the PCR magic happens.

You can think of it like a cauldron filled with a solution, where genetic wizards add the ingredients.

The ingredients are the DNA that we wish to multiply, an enzyme called Taq polymerase, specific primers, that bind to the DNA, and a mixture of free nucleotides - A, T, C and G. Throw everything in the thermal cycler, wave your magic wand, and the process begins.

So, let’s say that we have a long, double stranded DNA molecule, and we’re interested in the highlighted part. These two strands would be the template strands.

5’ - T T C A G G T C A C A G T C C T G T A T G C C T A T G T C C- 3’
3’ - A A G T C C A G T G T C A G G A C A T A C G G A T A C A G G- 5’

The first step of PCR is denaturation - meaning that we heat up our ingredients to exactly 96 degrees Celsius - almost as hot as boiling water.

This breaks open all bonds between the two strands of DNA, so that they can separate from one another.

The second step is called annealing. Here’s where we need primers, and for our highlighted sequence, the primers would look like this:

<----3’- C G G A T A C - 5’ 5’ - A G G T C A C - 3’ --->

During the annealing step, we cool everything down to around 55 degrees Celsius, and this allows the primers to bind to their complementary sequences on the single stranded DNA.


Polymerase chain reaction (PCR) and reverse-transcriptase PCR (RT-PCR) are both techniques used in molecular biology. Polymerase chain reaction (PCR) is used to amplify a single copy of a DNA sequence and generate thousands or millions of copies of a particular DNA segment. It has a wide range of applications, including the diagnosis of genetic diseases, the identification of bacteria and viruses, and the cloning and sequencing of genes.

On the other hand, reverse-transcriptase PCR (RT-PCR) is used to amplify and detect RNA molecules. It is based on the same principles as PCR but uses reverse transcriptase to convert RNA into cDNA (complementary DNA) before the PCR reaction. RT-PCR can be used to detect viral RNA, and to measure the levels of gene expression in cells.