LIFE 102 Lecture Notes - Dna Virus, Restriction Enzyme, Circular Rna
Document Summary
The viral dna that is integrated into the host genome is called a provirus. Unlike a prophage, a provirus remains a permanent resident of the host cell. The host"s dna polymerase transcribes the proviral dna into rna molecules. The rna molecules function both as mrna for synthesis of viral proteins and as genomes for new virus particles released from the cell. Viruses do not fit our definition of living organisms. Since viruses can reproduce only within cells, they probably evolved as bits of cellular nucleic acid. Candidates for the source of viral genomes are plasmids, circular dna in bacteria and yeasts, and transposons, small mobile dna segments. Plasmids, transposons, and viruses are all mobile genetic elements. Mimivirus, a double-stranded dna virus, is the largest virus yet discovered. There is controversy about whether this virus evolved before or after cells. Concept 19. 3: viruses, viroids, and prions are formidable pathogens in animals and plants.
