Subtopic 3.5: Gene Expression
Gene expression is a two-step process in which DNA is converted into a protein.
- The first step is DNA transcription to RNA. In this step, the information from the archival copy of DNA is imprinted into mRNA. The structure of RNA is a little different, it contains ribose instead of deoxyrybose, and the four bases that bind to it are cytosine (C), guanine (G), adenine (A) and uracil (U). During transcription, DNA unfolds, and mRNA is created by pairing mRNA bases with the bases of DNA. In this process C in DNA translates to G, G to C, A to U, and T to A. After mRNA is transcripted, it is transported to the ribosome.
- The second step, protein translation occurs at the ribosome. During translation, the sequence of codons (triplets of bases) of mRNA is, with the help of tRNA, translated into a sequence of amino acids.
Gene expression seems to be a straightforward process, the mechanism that control the gene expression that causes most phenotypic differences in organisms.