Genetics Assignment: Paraphrase and a Summary
The nucleotides (codons) translation normally occurs in triplets. This process involves strict ribosome fidelity maintenance, and as a result the errors rate in reading of the frame is 10-3 to 10-4 (Dunkle and Dunham 2015; Hansen et al. 2003; Jenner et al. 2010). Still, as a result of mistake the genetic code may be programmed in an mRNA-specific manner, which means that some translating ribosomes are diverted to a wrong reading frame (Chen et al. 2014b; Márquez et al. 2004; Tinoco et al. 2013). It may also occur that ribosomes translate a contiguous polypeptide, omitting a stretch of nucleotides (Herret al. 2000a). As a result, the amount of information encoded in DNA or RNA increases and one more layer of translational layer is added.
60 mRNA gene of bacteriophage T4, which codes viral DNA topoisomerase subunit, is the best-documented case of programmed bypassing (Herr et al. 2000; Huang et al. 1988; Weiss et al. 1990). This process involves translation of codons 1-45 to a Gly GGA codon, during which half of the ribosomes stops at UAG stop codon and the other half resumes translation from a downstream Gly codon (Maldonado and Herr 1998). Meanwhile, the anticodon of the peptidyl-RNAGly2 (Gly-2) does not stop but disintegrates from mRNA and peptidyl-tRNA joins mRNA downstream at a GGA codon (Herr et al. 1999). Thus, the translation resumes at the codon 46 and continuous protein product is created from a discontinuous open reading frame (Wills 2010).
Summary
In this paragraph author analyses the results of experiment on translation of wild-type gene's codons in rotated and non-rotated states, highlighting the main tendencies of this process. The author assumes that first 40 codons demonstrate regular elongation rate. Codons from 40 to 45 gradually slow, while their lifetime increases up to seven times (15 s for each state). At codon 45 long rotated-state pause is observed and then the process of bypassing takes place, as the translation resumes instead of …
