Replication, Transcription, and Translation: Easy Guide to How Proteins Are Made
Have you ever wondered how your body is able to make the proteins it needs to function? It is all thanks to the code written in your DNA which can then be transcribed into RNA “code” and then translated into a protein. These proteins serve vital functions like enzymes that break down the food you eat!
Learn more about replication, transcription, and translation in our easy guide to how proteins are made!
Source: Teach Me Physiology, The Cell Cycle
What is replication?
Replication is the process by which cells create 2 identical copies of their DNA. It occurs during the S phase of the cell cycle. By duplicating the DNA, the cell is trying to make enough DNA for when it divides during mitosis.
Here are some keywords and definitions that may help you when understanding replication:
1. Semiconservative: One strand from the “old” DNA that is being copied is paired with the “new” strand that is being synthesized and remains as part of the replicated double-stranded DNA so replication is called “semiconservative”
2. Daughter strand: The “new” single-stranded DNA
3. Template strand: The “old” DNA which is still a part of one of the copies 4. RNA primer - short sequence of nucleotides that acts as a “starting line” for DNA polymerase
Source: Khan Academy
4. Leading strand: Strand that can continuously be synthesized from the 5’ → 3’ direction
5. Lagging strand: Strand that cannot be continuously synthesized from 5’ → 3’ and is instead synthesized in fragments and requires a little help from ligase
Key enzymes:
1. Helicase: Unzips the DNA so the other enzymes can access the nucleotide sequence
2. DNA primase: Enzyme responsible for making the RNA primer
3. DNA Polymerase: Adds nucleotides that are complementary to the template strand one at a time in the 5’ → 3’ direction
4. Ligase: “Glues” all the Okazaki fragments together
Source: Khan Academy
What is Transcription?
Transcription is the process by which DNA code gets copied into RNA code. It occurs whenever the cell needs a specific protein whose instructions are encoded in the DNA.
The key enzyme:
● RNA polymerases - use the DNA code as a template to link nucleotides together to form the RNA strand in the 5’ → 3’ direction
All bases in DNA and RNA are the same EXCEPT RNA has uracil (U) in place of DNA’s thymine (T)
The process:
1. Initiation: RNA polymerase finds the promotor region in the DNA code and begins transcribing after the promotor sequence
2. Elongation: RNA polymerase continues adding bases to the growing RNA chain in the 5’ → 3’ direction
3. Termination: RNA polymerase comes to the DNA’s termination sequence and stops adding new bases to the RNA strand and the RNA is released
Source: Khan Academy
What is Translation?
Translation is the process by which the RNA code that was made during transcription is used to form a protein.
Here are some keywords and definitions that may help you when understanding translation:
Codon: The 3 letter sequence carried in the mRNA which is complementary to the incoming tRNA
Anticodon: The 3 letter sequence carried in the tRNA which is complementary to the mRNA in the A site
Charged tRNA: tRNA with an amino acid bound to it
The process
1. Initiation: Once the ribosome assembles around the mRNA a charged tRNA will bing to the start codon (AUG)
2. Elongation: mRNA is read one codon at a time, and the amino acid matching each codon is added to a growing protein chain
3. Termination: when the mRNA that enters the A site has the stop codon (UAA, UGA, or UAG) the ribosome disassembles and the growing peptides is cleaved from the tRNA that was in the P site
Final Thoughts on How Proteins Are Made
In conclusion, replication is needed for the cell to have enough genetic material to pass on when it undergoes mitosis. Transcription and translation are needed to take the code initially written in DNA “language” and turn it into a protein that the cell needs to function
From this blog, you should be able to better understand how DNA copies itself in order to have enough during cell division. You should also be able to understand how the DNA is transcribed into RNA and then translated into a protein that can be used for vital functions in the body. Try creating your own study guide to help you remember the material!
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