Amino Acids are the subunits or the monomers of a protein. Proteins are macromolecules which are created by ribosomes, organelles that are found in every living organism. Proteins are created through a 2-step process that begins with the DNA housed in the nucleus of a cell.
Transcription is the first step of protein synthesis. In order for a protein to be created, instructions must be given for how many amino acids must compose the protein, which types of amino acids, and the overall order of the amino acids in the protein. These instructions are given by the DNA. The first step of transcription is initiation. During initiation, a molecule called RNA Polymerase binds to a sequence of DNA called a promoter. The promoter is located at the beginning of a gene, which holds genetic information that composes a specific trait or characteristic of an organism. Then, the RNA Polymerase separates the double-stranded DNA and uses one strand as the template strand. The second step of transcription is elongation. During elongation, RNA Polymerase will create a strand by reading the template strand. The strand will be the exact same as the non-template strand, or the strand that is not being read. This occurs because DNA is composed of four nucleotides: Adenine, Guanine, Cytosine, and Thymine. Adenine always pairs up with Thymine and Guanine with Cytosine. Thus, if given one side of nucleotides provided by the template strand, RNA Polymerase is able to create a strand identical to the non-template strand because the same pair of nucleotides always pair up with one another. The only difference in base pairings between the strand being created, which is referred to as messenger RNA or mRNA, is that mRNA and all RNA for that matter, use Uracil instead of Thymine. Thus, Adenine pairs with Uracil and vice versa. The third and final step of transcription is termination. Each gene will have a terminator sequence, indicating RNA Polymerase to stop transcribing any more nucleotides. Once the terminator sequence is read, the mRNA will be released and the RNA Polymerase will detach from the DNA sequence.
Translation is the second step of protein synthesis, which occurs in the ribosomes. The mRNA created from transcription now needs to be read in order to create a protein. Before we delve into the steps of transcription, however, let’s first understand what a codon is. A codon is a group of three nucleotides. One codon codes for one amino acid. There are 61 different codons, however, only 20 amino acids. This means that certain combinations of codons code for the same amino acid. Now back to the steps of translation. The first step of translation is initiation. During initiation, the mRNA created from transcription attaches to a ribosome. Transfer RNA or tRNA are the molecules that read mRNA. Each tRNA has an anticodon, which are a set of three nucleotides that bind to a set of three matching nucleotides on the mRNA, also known as a codon. Each tRNA also has an amino acid attached to it. Once the tRNA anticodon binds to the mRNA codon, the amino acid will be attached with the growing chain of amino acids. Then, the tRNA will detach from the mRNA and the process repeats. The first codon read is the start codon, which is associated with the amino acid Methionine. During the second step of translation, elongation, the process of tRNA anticodon attaching to the mRNA codon, adding the appropriate amino acid attached to the tRNA to the growing amino acid chain, and the tRNA detaching repeats until the final step, termination. During termination, the stop codon is read. Finally, the amino acid chain detaches, creating a protein that can be used in the cell and body.
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