![]() ![]() The regulatory or promoter region is upstream of the transcriptional start and contains regulatory elements such as: Figure 11.2: Schematic view of a eukaryotic gene structure. The transcribed region is typically (but not always) downstream of the transcriptional start and contains the following DNA elements: a 5ʼ cap site (required for maturation of mRNA), translational start (AUG), introns and exons, and the polyadenylation site (figure 11.2). These are specific locations on a chromosome that are composed of a transcribed region and a regulatory (or promoter) region. The chromosome is organized into functional units call genes. The transcribed mRNA will serve as the template for protein translation. The 5ʼ to 3ʼ strand of a DNA sequence functions as the coding ( nontemplate) strand for the process of transcription such that the transcribed product will be identical to the coding strand, except for the insertion of uracil for thymidine (figure 11.1). Unlike DNA synthesis, which only occurs during the S phase of the cell cycle, transcription and translation are continuous processes within the cell. However, the translation to protein is still systematic and colinear. The translation to protein is a bit more complex because three mRNA nucleotides correspond to one amino acid in the polypeptide sequence. ![]() The copying of DNA to RNA is relatively straightforward, with one nucleotide being added to the mRNA strand for every nucleotide read in the DNA strand. ![]() Because the information stored in DNA is so central to cellular function, it makes intuitive sense that the cell would make mRNA copies of this information for protein synthesis, while keeping the DNA itself intact and protected. The decoding of one molecule to another is performed by specific proteins and RNAs. The flow of genetic information in cells from DNA to mRNA to protein is described by the central dogma, which states that genes specify the sequence of mRNAs, which in turn specify the sequence of amino acids making up all proteins. ![]()
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