replication

Examples of replication in the following topics:

• Viral Replication and Gene Expression

  • RNA viruses are classified into distinct groups depending on their genome and mode of replication.
  • Replication of viruses primarily involves the multiplication of the viral genome.
  • Replication also involves synthesis of viral messenger RNA (mRNA) from "early" genes (with exceptions for positive sense RNA viruses), viral protein synthesis, possible assembly of viral proteins, then viral genome replication mediated by early or regulatory protein expression.
  • Viral replication usually takes place in the cytoplasm .
  • Viruses that replicate via RNA intermediates need an RNA-dependent RNA-polymerase to replicate their RNA, but animal cells do not seem to possess a suitable enzyme.

• Chromosomes and DNA Replication in the Archaea

  • The cell division process is controlled by the cell cycle; the chromosomes within the Archaea are replicated to produce two daughter chromosomes.
  • The circular chromosomes contain multiple origins of replication, using DNA polymerases that resemble eukaryotic enzymes.
  • DNA replication, similar in all systems, involves initiation, elongation, and termination.
  • The replication of DNA, beginning at the origins of replication present on the circular chromosomes, requires initiator proteins.
  • The DNA replication system in Archaea, similar to all systems, requires a free 3'OH group before synthesis is initiated.

• Replication of Herpes Simplex Virus

  • Herpes replication entails three phases: gene transcription, viral assembly in the nucleus, and budding through the nuclear membrane.
  • The early proteins transcribed are used in the regulation of genetic replication of the virus.
  • The virion host shutoff protein (VHS or UL41) is very important to viral replication.
  • This enzyme shuts off protein synthesis in the host, degrades host mRNA, helps in viral replication, and regulates gene expression of viral proteins.
  • An enzyme shuts off protein synthesis in the host, degrades host mRNA, helps in viral replication, and regulates gene expression of viral proteins.

• Replication of Double-Stranded DNA Viruses of Animals

  • Viruses must first get into the cell before viral replication can occur.
  • However, in either cases, replication of the viral genome is highly dependent on a cellular state permissive to DNA replication and, thus, on the cell cycle.
  • Polyomaviruses, adenoviruses, and herpesviruses are all nuclear-replicating DNA viruses, each with their own specific approaches to replication.
  • Polyomaviruses replicate in the nucleus of the host.
  • Adenoviruses possess a linear dsDNA genome and are able to replicate in the nucleus of vertebrate cells using the host’s replication machinery.

• Viral Identification

  • The genetic material within virus particles and the method by which the material is replicated vary considerably between different types of viruses.
  • DNA viruses: The genome replication of most DNA viruses takes place in the cell's nucleus.
  • RNA viruses: Replication usually takes place in the cytoplasm.
  • RNA viruses can be placed into four different groups, depending on their modes of replication.
  • Reverse transcribing viruses with RNA genomes (retroviruses), use a DNA intermediate to replicate, whereas those with DNA genomes (pararetroviruses) use an RNA intermediate during genome replication.

• General Features of Virus Replication

  • Virologists describe the formation of viruses during the infection process in target host cells as viral replication.
  • Viruses must first penetrate and enter the cell before viral replication can occur.
  • Replication between viruses is varied and depends on the type of genes involved.
  • Replication of viruses depends on the multiplication of the genome.
  • Whenever the host divides, the viral genome is also replicated.

• Replicative Cycle of Influenza A

  • Influenza A follows the typical life cycle of most influenza virus: infection and replication are a multi-step process.
  • The infection and replication is a multi-step process:
  • Drugs that inhibit neuraminidase, such as oseltamivir, therefore prevent the release of new infectious viruses and halt viral replication.
  • Host invasion and replication cycle of an influenza virus.
  • Contrast the roles of hemagglutinin and neuraminidase throughout the major stages of the replicative cycle of influenza A virus

• Medical Importance of Viruses

  • Viruses are obligate intracellular parasites that hijack a host cell's machinery to replicate, thereby causing disease.
  • Amid this diversity, viruses with similar genome organizations exhibit major conserved themes in their replication strategies.
  • Once inside a cell, all viruses must uncoat, replicate, and transcribe their genomes, and then repackage their genomes into viral progeny that are released from cells.
  • RNA viruses in particular must coordinate the switch between plus and minus strand synthesis and between replication and transcription while protecting their genomes from cellular nucleases.
  • Because of the conserved nature of a virus's intracellular life cycle, fundamental advances in our understanding of replication have come from viruses that infect both animal and non-animal hosts.

• Inhibiting Nucleic Acid Synthesis

  • Other antimicrobial drugs interfere with DNA replication, the biological process that occurs in all living organisms and copies their DNA and is the basis for biological inheritance.
  • In a cell, DNA replication begins at specific locations in the genome, called "origins. " Uncoiling of DNA at the origin, and synthesis of new strands, forms a replication fork.
  • DNA replication, like all biological polymerization processes, proceeds in three enzymatically catalyzed and coordinated steps: initiation, elongation and termination.
  • Any of the steps in the process of DNA replication can be targeted by antimicrobial drugs.

• Selection

  • This will generate a population of organisms in which recombinant DNA molecules are replicated along with the host DNA.
  • This process takes advantage of the fact that a single bacterial cell can be induced to take up and replicate a single recombinant DNA molecule.
  • Therefore, if any segment of DNA from any organism is inserted into a DNA segment containing the molecular sequences required for DNA replication, and the resulting recombinant DNA is introduced into the organism from which the replication sequences were obtained, then the foreign DNA will be replicated along with the host cell's DNA in the transgenic organism.
  • Molecular cloning is similar to polymerase chain reaction (PCR) in that it permits the replication of a specific DNA sequence.
  • The fundamental difference between the two methods is that molecular cloning involves replication of the DNA in a living microorganism, while PCR replicates DNA in an in vitro solution, free of living cells.