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Genes are not linear sequences of DNA that directly correspond one-to-one with their protein counterparts. Moreover, scientists now know that not all transcribed RNA molecules, or transcripts,...
-In living cells, RNA is usually a double-stranded molecule, while DNA can often be single-stranded. In viruses called retroviruses, the genetic information is contained in RNA; these viruses have no DNA. These viruses also have an enzyme called reverse transcriptase. What is its function?
For example, circoviruses get by with only two genes: one to encode the capsid protein that will protect and deliver the genome in the infectious virus, and a replicase protein that hijacks cellular polymerases to create new copies of the viral single-stranded DNA genome.
The flow of genetic information in cells from DNA to mRNA to protein is described by the Central Dogma of molecular biology (Figure 16.2). When a cell needs a particular protein, the gene that codes for that protein is activated and a single-stranded mRNA copy is made of the gene, in a process called tr a nscription .
8 maj 2024 · Positive-strand RNA [(+)RNA] viruses include pandemic SARS-CoV-2, tumor-inducing hepatitis C virus, debilitating chikungunya virus (CHIKV), lethal encephalitis viruses, and many other major pathogens.
Both of these examples show a high density of coding information. In influenza virus, genes 7 and 8 both encode two proteins in overlapping reading frames. In geminiviruses, both strands of the virus DNA found in infected cells contain coding information, some of which is present in overlapping reading frames.
Reverse genetics begins with a cloned gene, a protein with interesting properties that has been isolated from a cell, or simply a genome sequence. If the starting point is a protein, the gene encoding it is first identified and, if necessary, its nucleotide sequence is determined.
