DNA Transcription

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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…
The polymerase travels along the DNA template strand running antiparallel. Reading each base in the template DNA strand, it attaches a complementary RNA nucleotide to the new RNA strand that grows form 5’ to 3’. The RNA transcript is nearly identical to the non-template strand of DNA with an exception of the RNA base uracil (U) in place of the DNA base thymine (T). RNA polymerase at the promoter region is able to break open the DNA double helix making it able to increasingly move down the template. Once a section is transcribed, the two DNA strands re-form the double helix behind the transcription bubble leaving the RNA transcript dangle behind. RNA polymerase will continue to transcribe until it receives a signal to …show more content…
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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