Genetic code open reading frames

The EDITSEQ application allows you to manually enter DNA or protein sequence information into your computer. This application has several features that make it useful to the research scientist. First, it can identify open reading frames (possible gene sequences) within a DNA sequence. Second, it can provide the percent base composition (A,G,C,T), the percent GC, the percent AT, and the melting temperature of the entire sequence or a small subset of that sequence. Third, EDITSEQ can translate a nucleotide sequence into a protein sequence. Finally, the application is capable of translating or reverse translating a nucleotide sequence of interest using codes other than the standard genetic code. 

The first step in translation is the assembly of the initiation complex. In bacteria, this is done in a three-step process that involves the initiation factors IF-1, IF-2, and IF-3, the 30S and 50S ribosomal subunits, and the hydrolysis of GTP. As shown in Figure 26.10, the first step is the formation of a preinitiation complex consisting of IF-1, IF-3, and the 30S ribosomal subunit. This preinitiation complex binds with high affinity to a translational start site on the mRNA transcript which is close to the 50 end and includes the first codon of the open-reading frame. This codon is called the initiation codon and it is usually AUG, which specifies the amino-acid methionine in the genetic code (Fig. 26.6). 

Translation of the consensus cDNA sequence using the standard genetic code results in a single open reading frame coding for human factor XII. The derived amino acid sequence agreed well... 

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