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Principles of Biomedical Science - Unit 3.1.1 to Unit 3.2.1 COMPLETE Study Guide - Preparation for Unit 3 Quiz Final

Terms in this set (20)

Protein synthesis, or the process by which gene expression happens, can be divided into two main steps: transcription and translation. In that, the genes that are present in the double helix of DNA are transferred, or moved, to form proteins, and in this parent strand, there is a region called a promoter region, which indicates to the DNA polymerase where to bind -- the initiation stage. As this is ongoing, the DNA polymerase unzips the DNA double helix into two separate strands, where there is a complementary pairing of the mRNA bases -- the enlargement stage. (A == U, C === G)
In order for this event to finish, there is a location called a terminator region, in the DNA, and once the DNA polymerase approaches this place, the constructed mRNA is released -- the terminating stage.
Alongside with that, there are portions within the mRNA called extrons that code for proteins, and introns that do not code for any proteins, and hence, in the case of intron splicing, the spliceosomes remove the unwanted introns from the mRNA.
Thus, with the addition of a 5' cap and a 3' poly-A tail, a mature mRNA strand is formed, whence it moves into the cytoplasm of the cell, to be converted into a protein in translation.
In this stage, the mRNA is used as a template, and for each three letters of nitrogenous bases, called codons, there is a complementary tRNA strand produced, when the ribosome affixes itself to the mRNA. With the tRNA, there is a corresponding amino acid, and as each of them bind with the codons of mRNA in the E, P, and A places of the ribosome subunit, the amino acid is released, where it forms peptide bonds with other amino acids. For a while, this process continues, until the ribosome reaches a stop codon, which signals the end of the process, in which case the polypeptide chain of amino acids is released to form a protein.