The body is made up of cells. Inside the cell, we can find nucleic acid. Nucleic acids are composed of what we call nucleotides. These nucleotides are the monomers of nucleic acids. They consist of several different things like sugar, phosphate and a nitrogenous base. The best-known nucleotide itself is ATP (Adenosine Triphosphate). ATP is vital because it is the energy currency of the cell.
To better understand mRNA let us discuss DNA and RNA. These two have a vital role in producing mRNA.
Nucleic acids have two main classes: DNA and RNA. Let us break down the difference between the two.
| DNA or deoxyribonucleic acid | RNA or ribonucleic acid |
| – is a double helical structure that contains the hereditary material in living organisms. -DNA is much bigger than RNA. – contains deoxyribose as its sugar. -consists of four nitrogenous bases: Adenine (A), Cytosine (C), Guanine (G), and Thymine (T). | -is a single helix. – RNA is much smaller than DNA. – contains ribose as its sugar. – Also consists of four nitrogenous bases. Instead of Thymine, RNA has Uracil (U), Adenine (A), Cytosine (C), and Guanine (G). |
Note: DNA has genetic information codes for everything discovered in a given organism and it can make a copy of itself.
Let’s take a look at the cell.
At the center of the cell, we can see the nucleus. We can find the DNA inside the nucleus. Because the DNA is too large to leave the nucleus of the cell, it will always remain there.
Replication is the process by which DNA copies itself. DNA can also direct the synthesis of RNA in the nucleus, through a process known as transcription.
Transcription is the process of creating RNA from DNA. Transcription, like DNA replication, occurs within the cell’s nucleus. Once RNA is synthesized from DNA, it can exit the nucleus via nuclear pores and enter the cytoplasm. Protein synthesis can take place here, on a ribosome. The translation is a process of converting RNA to protein.
These three processes are known as biology’s central dogma, in which we take instructions from DNA and convert them into a functional product by going from DNA to RNA to protein.
To better understand the differences between such three phases, refer to the table below:
| Replication | Transcription | Translation |
| – DNA replicates itself. – This process occurs in the nucleus. – It generates two identical DNA strands. – This process is needed only when the cell replicates. | – The synthesis of RNA from DNA. – Process occurs in the nucleus. – mRNA is produced and leaves the nucleus. | – It is responsible for the conversion of mRNA to protein. – This process occurs in the cytoplasm on a ribosome. Ribosomes can be free floating or attached to the rough endoplasmic reticulum. – Produces proteins. |
What is mRNA?
- mRNA is an essential component in making proteins. Without mRNA, we would not have the code to make the specific proteins that are found within the body.
Where does mRNA come from?
The RNA that makes the protein during the process of translation is mRNA. When RNA is transcribed from DNA to make protein, only a small portion of the DNA is transcribed. Therefore, RNA products are much smaller than DNA itself. And that’s how RNA can leave the cell’s nucleus.
When RNA is first transcribed from DNA it is referred to as pre-mRNA or a precursor mRNA. In order for pre-mRNA to become mRNA, it needs to be processed through a series of steps.
In the first step, all the introns have to be removed. Keeping all the exons together. These exons are known as the protein-coding region. The removal of these introns or the splicing that occurs to put these exons together also allow for the diversity that we see within mRNA allows for different proteins to be made. Furthermore, the addition of a five prime cap and a three prime poly tail. Once these modifications have been made the mRNA is then now ready to move from the nucleus into the cytoplasm in order for protein synthesis to occur.
Once this mature mRNA leaves the nucleus and enters into the cytoplasm of the cell it will attach to an organelle known as a ribosome (made up of rRNA).
Three sub-units of the ribosome binding sites:
- Amino acid site
- Polypeptide site
- Exit site
The first tRNA molecule is going to come in and bind with Adenine (A), Uracil (U) and Guanine (G). The mRNA will become triplets or referred to as codons. The tRNA has an anticodon match up with the codon of the RNA.
Note: The AUG of the mRNA is the start codon which begins the process of translation, the tRNA is going to come in and bind.
These tRNAs continue to come into the ribosome and build up the amino acid chain, matching amino acids to their respective codons, which creates a polypeptide. Once a stop codon is reached, the amino acid chain or polypeptide chain, will be released from the ribosomes.
There are three different stop codons or termination codons that can be found on the mRNA: UAA, UAG and UGA. These are codons that the tRNA cannot recognize and it allows the release of the protein.
Once the protein is made it can now do its job. A lot of proteins do need post-translational modifications, in which, things will be added onto that protein. The proteins also need to be folded into their proper shape in order to function correctly.
Below is a video I have made on this topic:
Learning Biology with Dr. Vanessa, LLC 