Index >> Microbial Genetics >> Merits and Demerits of Viruses and Bacteria as the Materials for Genetic Experimentation

 The relative simplicity of microorganisms such as viruses offers the best opportunity for studying gene structure and function at the molecular level. Most microorganisms have short generation period. For example, some bacteria divide about once every 30 minutes. Beginning with a single cell, thirty generations can elapse within fifteen hours, producing approximately a billion progeny cell. All of the asexual descendants of a single bacterium are genetically identical (barring mutation) and are referred to as a clone or colony visible to the naked eye when grown on solid medium such as an agar plate.
One of the disadvantages of using, some microorganisms for genetic studies is the relative dearth of regular recombinational events.

Further, though they are called haploid organisms, but most bacteria are actually multinucleate. A delay in phenotypic expression of some mutants is to be anticipated until nuclear and bacterial divisions can seggregate out tile mutated nuclei from the others to form a pure clone. The more nuclei per cell the longer the delay is expected to be. Even viruses, too small to be seen with the light microscope, can show variation in the type of cell they will parasitize (host range) in the rapidity with which they cause rupturing of its host cell (lysis), and in the shape of the "hole" (plaque) which appears in a confluent growth of host cells on solid media. These variations may become apparent to the investigator only after several recombinational events or "rounds of matings" have occurred, so that population dynamics; may become a source of confusion in genetic analysis. Moreover, bacteria and viruses do not possess easily visible chromosomes comparable to those of higher organisms. But many modern micro-techniques and electron microscopy have greatly aided the geneticists to understand the different genetical aspects of viruses and bacteria with great precision.