genome fusion

Examples of genome fusion in the following topics:

• Endosymbiotic Theory and the Evolution of Eukaryotes

  • Genome fusion occurs during endosymbiosis, which is the mechanism proposed as responsible for the first eukaryotic cells.
  • Scientists believe the ultimate event in HGT (horizontal gene transfer) occurs through genome fusion between different species when two symbiotic organisms become endosymbiotic.
  • Within the past decade, the process of genome fusion by endosymbiosis has been proposed to be responsible for the evolution of the first eukaryotic cells .
  • More controversial is the proposal that (a) the eukaryotic nucleus resulted from the fusion of archaeal and bacterial genomes; and that (b) Gram-negative bacteria, which have two membranes, resulted from the fusion of Archaea and Gram-positive bacteria, each of which has a single membrane.
  • Describe the genome fusion hypothesis and its relationship to the evolution of eukaryotes

• Limitations to the Classic Model of Phylogenetic Trees

  • Finally, as an example of the ultimate gene transfer, theories of genome fusion between symbiotic or endosymbiotic organisms have been proposed to explain an event of great importance: the evolution of the first eukaryotic cell, without which humans could not have come into existence.

• Web, Network, and Ring of Life Models

  • This structure is proposed as the best fit for data from extensive DNA analyses; the ring model is the only one that adequately takes HGT and genomic fusion into account.

• Genomic Similiarities between Distant Species

  • Genomic similarities between distant species can be established via analysis of genomes using advanced technology.
  • These technologies have established genomic similarities between distant species by establishing genetic distances .
  • In addition, the mechanisms by which genomic similarities between distant species occur can include horizontal gene transfer.
  • Finally, as an example of the ultimate gene transfer, theories of genome fusion between symbiotic or endosymbiotic organisms have been proposed to explain an event of great importance—the evolution of the first eukaryotic cell, without which humans could not have come into existence.
  • Discuss the evolutionary implications of observed genome similarities between distant species

• Vaccines and Anti-Viral Drugs for Treatment

  • Drugs have been developed that inhibit the fusion of the HIV viral envelope with the plasma membrane of the host cell (fusion inhibitors), the conversion of its RNA genome into double-stranded DNA (reverse transcriptase inhibitors), the integration of the viral DNA into the host genome (integrase inhibitors), and the processing of viral proteins (protease inhibitors).
  • Viral contents are released into the cell where viral enzymes convert the single-stranded RNA genome into DNA and incorporate it into the host genome.

• Fertilization

  • The fusion of these two membranes creates an opening through which the sperm nucleus is transferred into the ovum.
  • Fusion between the oocyte plasma membrane and sperm follows and allows the sperm nucleus, centriole, and flagellum, but not the mitochondria, to enter the oocyte.
  • The nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.

• Animal Viruses

  • The viral genome is then "injected" into the host cell through these channels in a manner analogous to that used by many bacteriophages.
  • Enveloped viruses also have two ways of entering cells after binding to their receptors: receptor-mediated endocytosis and fusion.
  • On the other hand, fusion only occurs with enveloped virions.
  • These viruses, which include HIV among others, use special fusion proteins in their envelopes to cause the envelope to fuse with the plasma membrane of the cell, thus releasing the genome and capsid of the virus into the cell cytoplasm.
  • After making their proteins and copying their genomes, animal viruses complete the assembly of new virions and exit the cell.

• Uses of Genome Sequences

  • Genome sequences and expression can be analyzed using DNA microarrays, which can contribute to detection of disease and genetic disorders.
  • Almost one million genotypic abnormalities can be discovered using microarrays, whereas whole-genome sequencing can provide information about all six billion base pairs in the human genome.
  • Although the study of medical applications of genome sequencing is interesting, this discipline tends to dwell on abnormal gene function.
  • Genomics is still in its infancy, although someday it may become routine to use whole-genome sequencing to screen every newborn to detect genetic abnormalities.
  • DNA microarrays can be used to analyze gene expression within the genome.

• Advantages and Disadvantages of Sexual Reproduction

  • This is the ultimate source of variation in sexual organisms, but, in addition, those different mutations are continually reshuffled from one generation to the next when different parents combine their unique genomes and the genes are mixed into different combinations by the process of meiosis.
  • Fertilization, the fusion of haploid gametes from two individuals, restores the diploid condition.
  • Fusion of the gametes gives rise to a fertilized egg cell, or zygote.

• Use of Whole-Genome Sequences of Model Organisms

  • The first genome to be completely sequenced was of a bacterial virus, the bacteriophage fx174 (5368 base pairs).
  • Several other organelle and viral genomes were later sequenced.
  • It took this long because it was 60 times bigger than any other genome that had been sequenced at that point.
  • Having entire genomes sequenced aids these research efforts.
  • The process of attaching biological information to gene sequences is called genome annotation.