Radiation Resistance

Many hypotheses have been proposed to explain the highefficiency repair, including a ringlike condensed chromosome structure that could restrict fragment DNA diffusion, a high Mn2+ concentration that can scavenge hydroxyl radicals, an enhanced capacity for replication fork repair, and the presence of multiple genome copies to facilitate recombinational DNA repair. Mechanisms that reduce the level of protein oxidation have emerged as major contributors to extreme radiation resistance, with possible contributions from novel adaptations of DNA repair systems.

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Thanks, this is helpful. However, I can't open an attachment. Is there any other way to access this information?

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I have a Question about my report in zoology Compare the circulatory system and vascular system of fishes, amphibians, reptiles, eves and mammals can you help me?

The possible theories were of great help, but I am still lost on a potential experiment to help solve this. Any help?

There are several hypotheses that have been proposed to explain the high level of ionizing radiation resistance/high efficiency repair.  Hypotheses include a high manganese concentration that can act as antioxidants, a ring-like condensed chromosome structure that could restrict fragment DNA diffusion, an enhanced capacity for replication fork repair, and the presence of multiple genome copies to facilitate recombinational DNA repair.  Mechanisms that reduce the level of protein oxidation have emerged as major contributors to extreme radiation resistance, with possible contributions from novel adaptations of DNA repair systems.  An example of an experiment to test one of these hypotheses (high manganese concentration that can act as antioxidants, for example) would be to take a culture Escherichia coli and use it to try to create radiation-resistant strains of E. coli by pumping up their levels of manganese.  If they become highly resistant to ionizing radiation, then a conclusion can be made that high levels of manganese contribute to the bacterium’s resistance to ionizing radiation.

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The name Deinococcus radiodurans derives from the Ancient Greek deinos and kokkos meaning "terrible grain/berry" and the Latin radius and durare, meaning "radiation surviving". The species was formerly called Micrococcus radiodurans. As a consequence of its hardiness, it has been nicknamed Conan the Bacterium. Initially, it was placed in the genus Micrococcus. After evaluation of ribosomal RNA sequences and other evidence, it was placed in its own genus Deinococcus, which is closely related to the genus Thermus of heat-resistant bacteria; the group consisting of the two is accordingly known as Deinococcus-Thermus.  Deinococcus is the only genus in the order Deinococcales.  All known members of the genus are radioresistant.  Deinococcus radiodurans has a unique quality in which it can repair both single- and double-stranded DNA. When a damage is apparent to the cell, it brings it into a compartmental ring-like structure, where the DNA is repaired and then is able to fuse the nucleoids from the outside of the compartment with the damaged DNA.
D. radiodurans is a rather large, spherical bacterium, with a diameter of 1.5 to 3.5 µm. Four cells normally stick together, forming a tetrad. The bacteria are easily cultured and do not appear to cause disease.  Colonies are smooth, convex, and pink to red in color. The cells stain Gram positive, although its cell envelope is unusual and is reminiscent of the cell walls of Gram negative bacteria. ]D. radiodurans is capable of withstanding an acute dose of 5,000 Gy (500,000 rad) of ionizing radiation with almost no loss of viability, and an acute dose of 15,000 Gy with 37% viability. [A dose of 5,000 Gy is estimated to introduce several hundred double-strand breaks (DSBs) into the organism's DNA (~0.005 DSB/Gy/Mbp (haploid genome)). For comparison, a chest X-ray or Apollo mission involves about 1 mGy, 5 Gy can kill a human, 200-800 Gy will kill E. coli, and over 4,000 Gy will kill the radiation-resistant tardigrade.