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---TRANSCRIPT---
Thanks for stopping by, this is 2 Minute Classroom and today we are going to learn all about transcription and translation. You’ll learn everything you need to know about how DNA serves as a template for RNA and how that RNA leads to protein production in eukaryotes.

Transcription is the process of taking a section of DNA and copying or transcribing it into RNA. It’s similar to you taking a picture of the page of a recipe book with your phone for example. You don’t have the whole recipe book in that picture, but you do have the information from that page. The RNA is a “picture” of a small section of DNA, but not the whole strand of DNA.

Let’s look at how the process of transcription occurs. There are 3 main steps, initiation, elongation, and termination.

During initiation, A section of DNA called the “promoter” signals where and when transcription takes place. The protein RNA Polymerase finds this promoter and separates the double stranded DNA. Once separated, the RNA polymerase binds to the DNA and begins transcribing a section on one strand (the template strand) of the DNA into RNA. The promoter identifies the section to be copied, but is not copied itself.

Elongation occurs as the RNA polymerase reads the template strand and builds a complementary RNA strand by bringing the appropriate nucleotides together. This RNA strand is almost identical to the non-template DNA strand, except that the Thymine in DNA are replaced with Uracil in the RNA strand.

To complete the process, we have termination. Just as there is a section of DNA to signal where transcription starts, there is a section of DNA that signals where transcription stops. This section of DNA is called the terminator sequence. Once RNA polymerase reaches the terminator sequence, the RNA strand separates from the template DNA.

After termination, the newly constructed RNA strand undergoes some moderations to remove sections that will not be translated. The RNA then leaves the nucleus to be translated into a protein. This signifies the end of transcription and brings us to translation.

Translation is the process of building a protein-based on an RNA blueprint. This process takes place on ribosomes, which are either embedded in the Rough ER or free floating in the cell. If you are unfamiliar with ribosomes or just want a refresher, I will link an excellent video here and in the description below. Using the example of a picture of a recipe from a cookbook, translation would be like the process of making the cookies using the image of the recipe on your phone. The RNA just contains information used to build the final product.

Before we dive further into translation though, we need a crash course in codons. Codons are a sequence of three nucleotides that code for a specific amino acid, the building blocks of proteins. Remember, RNA has the nucleotides U, C, A, and G. Any pairing of three RNA nucleotides will code for a specific amino acid. There are 61 codons that each code for one of 20 amino acids. These codons are well documented, making your life much easier.

Once the RNA leaves the nucleus, it attaches to a ribosome and translation begins. The ribosome “reads” the RNA strand until it finds the nucleotides A-U-G, this is the “start” codon and that signals for protein synthesis to begin.

The amino acids are brought to the ribosome by tRNA and linked together to form the polypeptide chain that will become a functioning protein. Each tRNA has a specific section called the anti-codon which matches up with the codon on the RNA being translated.

This process continues with the ribosome reading three nucleotides at a time and bringing in the appropriate tRNA with its associated amino acid. The process stops when the ribosome reaches one of three “Stop” codons: U-A-A, U-A-G or U-G-A. The stop codons do not code for an amino acid, instead, they signal to the ribosome to stop translation the release the polypeptide chain for further modification prior to becoming a functioning protein.

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