Before beginning the explanation between RNA and DNA, it is important to determine the variations between DNA and RNA. DNA and RNA are both nucleotide polymers, however, there are some distinct differences. Both have a helix type structure, but DNA shows the double helix structure whereas RNA is single-stranded. DNA has the nitrogen bases A,T,C, and G, but RNA doesn't have T (thymine). Instead, the T is replaced with a U (uracil) in RNA. Also, DNA has one less O on the 5' sugar in comparison to RNA. This is where the "DEOXY"ribose reference comes from for DNA.
Transcription:
Transcription is the first step of the protein synthesis. It occurs in the nucleus of the cell which is where all of the DNA is stored. The DNA are in "another language" that cannot be read to produce proteins. This is how transcription plays its role. In transcription, the DNA in unzipped by a new enzyme, RNA polymerase. This is different from the helicase in DNA replication. Carrying on, the RNA polymerase runs along the DNA strands and adds complementary RNA nucleotides to the DNA. (This is where the role of the U, uracil, comes in instead of T. When the single helix mRNA strand is finished, it will move apart and seperate from the DNA and the DNA will re-zip into a double helix.
In a eukaryotic cell, when this is done, the mRNA will go through processing. In the mRNA processing, a G (guanine) cap will be added to the front and a Poly-A tail. (Poly-a simply means multiple A's) These are placed on the mRNA in order to prevent the nucleases outside of the nucleus from consuming them. This is because typically these enzymes will have the same reaction as if they were encountering a virus. This way, the poly-A tail and G cap can prevent the destruction of the mRNA. Then this strand will be spliced and the introns (non-coders) will be removed and the remaining exons (coders) will be spliced together. The completed mRNA strand will have groups of 3 nucleotides which are known as codons. The AUG codon in mRNA is usually the start codon that codes for the amino acid: met, or methionine.
Translation:
Translation will begin when the messenger RNA moves out of the nucleus area and into the cytoplasm. 3 types of RNA now become involved in the process: mRNA, tRNA, rRNA. mRNA, as stated before is known as messenger RNA. The tRNA is the transfer RNA. Finally, the rRNA is the ribosomal RNA. The part of the rRNA known as the large ribosomal unit has an A site and a P site. This is where the polypeptides, long chains of amino acids, synthesize and elongate. The rRNA is a factory as the tRNA is to a worker. The tRNA go through the cell and bring back amino acids from their attachment sites. The tRNA also carriers an anticodon which is the complementary sequence for a certain codon. The tRNA picks up the specific amino acid based on the code it contains. Then the translation of mRNA through the rRNA occurs. AUG, the first codon, begins with the A site. Then, the tRNA, with the matching anticodon of UAC, will meet with the start codon and bring back the correct amino acid, met (methionine).
Here is a chart that represents the matching amino acid for the appropriate codes:
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