Eukaryotic Synthesis

As described in the central dogma of biology, information from a gene can be used to build a protein in a two-step process. Transcription is considered to be the first step of gene expression. It is known to be the process of making a copy of genetic information stored in a DNA strand into a complementary strand of messenger RNA (mRNA). The process of eukaryotic transcription can be separated into three phases, initiation, elongation and termination. This complex process involves various cell signaling methods as well as the activity of many enzymes. Genes are segments of DNA nucleotides located on a chromosome that contains the codes for the construction of individual proteins. They are found in the nucleus of cells where transcription first …show more content…
DNA produced mRNA in transcription in which the mRNA will be decoded to build a polypeptide chain of amino acids in translation. This process is one of the most complicated tasks that cells can perform using a great deal of energy to do so. To translate mRNA into a protein it requires a series of detailed steps and molecules including initiation, elongation and termination.
After transcription is complete the mRNA leaves the nucleus and travels into the cytoplasm. Translation may occur in either the cytoplasm or the rough endoplasmic reticulum. Two molecular factors that play a key role in translation are transfer RNAs (tRNAs) and ribosomes. tRNA is a RNA molecule that carries amino acids to the ribosomes where they will be added to a growing polypeptide chain. They contain a base pair of 3 amino acids that can bind to the complementary mRNA codons. The relationship between codons and amino acids is known as the genetic code where it defines how sequences of codons specify which amino acid will be added next. Ribosomes are large structures within the cytoplasm that house the translation process and catalyze some of its steps. These structures are made up of ribosomal RNA (rRNA) and protein subunits that provide a space for tRNA to bind to an mRNA template. Each ribosome contains 3 binding sites known as the A,
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The tRNA start codon AUG is positioned at the P site of the fully assembled ribosome where the second complementary codon lies in the A site waiting to be bound. Guanosine triphosphate (GTP) hydrolysis serves as an energy source for the specific matching of tRNAs. As the ribosome moves along the mRNA strand in a 5’ to 3’ direction, in the P site, tRNA binds to the complimentary codons of mRNA adding their amino acids forming a polypeptide chain. Although, there are fewer tRNAs than codons which causes the wobbling effect which accepts less strict bindings allowing tRNA to translate more than one codon. Once the polypeptide bond has formed, the tRNA holding the polypeptide will shift from the A site to P site shifting the empty tRNA in the P site to the E site where it is released into the cytoplasm. GTP is also used as an energy source to make this translocation occur exposing the next codon in the A site. This cycle repeatedly happens until a stop codon reaches the A

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