9/20/2023 0 Comments Transcription translation stepsIn Class VII viruses the (+) RNA shown in blue (pregenome RNA) functions as a template for synthesis of DNA, some of which is used as a template for further transcription. A (+) RNA genome (dark blue) has the same sequence as the corresponding mRNA (green) the molecules are shown in different colors to indicate their different functions. Most of these viruses have either a (+) or a (–) strand genome. (+) and (–) strands are indicated for the ssDNA of the Class II viruses. (+) and (–) strands are not indicated for the dsDNA of the Class I viruses as the genomes of most of these viruses have open reading frames (ORFs) in both directions. (+) RNA and (+) DNA have the same sequence as the mRNA, and (–) RNA and (–) DNA have the sequence complementary to the mRNA (except that in DNA thymine replaces uracil). Because of distinct modes of transcription within the dsDNA and ssRNA categories a total of seven classes of viruses can be recognized ( Figure 6.1).įigure 6.1 Transcription of virus genomes. We have seen how there are four main categories of virus genome: dsDNA, ssDNA, dsRNA and ssRNA (Section 3.2). At the end of the chapter we point out some aspects of the processes that are different in bacterial cells. We start with an overview of virus transcription, and then we discuss these three “trans” processes in eukaryotic cells. We also discuss in this chapter the transport of virus proteins and RNAs to particular locations in infected cells. Transcription and translation are steps 3 and 4 of our generalized replication cycle (Section 5.1). ![]() For our purposes, transcription refers to the writing across of genetic information from a sequence of bases in a nucleic acid to the complementary sequence in messenger RNA (mRNA), while translation converts the genetic information from the language of bases in nucleic acids to the language of amino acids in proteins. In this chapter we deal with three terms derived from the Latin trans, meaning across. 6.1 INTRODUCTION TO TRANSCRIPTION, TRANSLATION, AND TRANSPORT
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