Ggc Immunization: Fill & Download for Free

Thanks for the A2A.It’s important that we understand what a mutation is. Simply put, a mutation is a permanent change in a segment of DNA, including an error in the sequence of a single gene.A gene is a section of DNA that acts as a blueprint for the synthesis of a specific protein (some genes have other functions, but that’s not really important for this discussion). The “alphabet” of DNA (and therefore genes) contains four “letters”, A, T, C, G. These are abbreviations of molecules called nucleosides or bases. Each gene is a long sequence of As, Ts, Cs and Gs chemically bonded to one another. A string of three bases (like “TCA” or “GGC”, for example) is called a codon, and codes for one of the 20 amino acids that are the building blocks of all of the proteins in our body (including, importantly, all enzymes). A long string of codons, therefore, codes for a protein.It may surprise you to learn that molecular damage to DNA occurs millions of times per day per cell. Fortunately our cells have a remarkable, almost flawless DNA repair mechanism that identifies and corrects these errors before they become permanent.Occasionally, damage to one or more segments of DNA may occur that is not reparable; it is permanent. This is the definition of a mutation.For example, a base may be added to a gene’s sequence (insertion mutation) or removed from it (deletion mutation). One type of base can be converted to another, e.g., an A to a G (substitution mutation). Or a base may be altered chemically to some other molecule that doesn’t function as a base at all.Lots of mutations are much more complicated alterations of genetic sequences. For instance, some mutations can involve a shift of an entire stretch of DNA from one location to another.Some mutations can lead to the inability to synthesis a protein coded by the damaged gene. If this is a vital protein, the cell dies (lethal mutation).Other lethal mutations cause such extensive damage to DNA, it can’t accurately replicate, so a cell can’t properly divide and an entire potential line of daughter cells never develops. In this scenario, as cells within a tissue or organ reach the end of their lives, there are no healthy daughter cells to replace them; the entire organ may die. This is not a good thing.A mutation might result in just the opposite scenario: a cell that starts dividing uncontrollably, the mutation being passed on to all daughter cells, leading to a mass of cells all dividing and growing uncontrollably. This is how cancers develop. Again, not a good thing.Until now, we have been talking about mutations in the non-germ cells in our bodies (somatic cells). However, mutations can also occur in our germ cells (ova and sperm). If they are not fatal, they will be passed on during fertilization. Such nonlethal mutations can lead to childhood diseases, which might be fatal or may cause nonlethal diseases that allow the person to reach adulthood and pass the mutation on to future generations (the whole specialty of genetic diseases is devoted these types of disorders).Other germ cell mutations may be less deleterious, or (and this is rare) even beneficial and accumulate in the “gene pool” of a species. This is the basis for evolution.Outside agents that can cause mutations are called mutagens. These include agents that cause lethal mutations, leading to cell death. Other agents can induce cancer-causing mutations (carcinogens).Now, to address your question: Some types of high energy radiation, like X-rays, are indeed mutagenic and can cause cell death or carcinogenesis, depending on dose.Such high energy radiation, including x-rays and gamma rays, is also known as "ionizing radiation", because it has the energy to dislodge electrons from atoms inside living tissues. The resulting atoms have a positive charge (they're ions, hence "ionizing radiation").These free electrons can then damage DNA, either directly through interaction of the electron with a strand of DNA, or indirectly, by interacting with water, producing highly reactive hydroxyl radicals, which then interact with DNA. In either case, the result is always bad; nucleotide bases are altered or DNA strands break. In other words, we have a mutation.When talking about high doses of radiation, we know with a good deal of certainty what biological effects will occur for a given single dose of ionizing radiation (acute radiation syndrome). The types of DNA damage that occur at such high doses are the kind that prevent DNA replication and cell division. Those tissues that require the most robust cell turnover and division are the ones that are most easily injured by high dose radiation. These tissues include skin, bone marrow, the lining of the gut and the germ cells in ovaries and testes.A dose of 1-2 Grays (Gy) will injure gut cell DNA and cause nausea and vomiting within 6 hours.A dose of 2-6 Gy will lead to vomiting within 2 hours and diarrhea in 6-8 hours. Skin will also be affected, resulting in hair loss and skin burns and blistering within 1-4 weeks . The injury to bone marrow will lead to anemia with weakness and fatigue within 1-4 weeks. Also platelet production will be impaired, leading to easy brusing and bleeding. The death of white cell precursors in the marrow will suppress the immune system and impair the ability to fight infection.A dose of 6-9 Gy will produce the GI symptoms within an hour and anemia within a week. This dose is also high enough to injure brain cells, leading to confusion and disorientation within a week.A dose of 10 Gy or higher is enough to cause immediate coma as well as almost instant eradication of blood cells and the lining of the gut. This dose is not survivable.Fortunately, people are rarely exposed to the high doses of radiation discussed above. There are, though, some well-known cases of acute radiation sickness, notably the victims of the atomic bomb explosions at Hiroshima and Nagasaki. Also, pioneers in the study of ionizing radiation like Roentgen and Curie suffered some degree of radiation sickness as did workers in watch factories where radium was painted onto watch dials to make them luminous. Other victims of acute radiation injury include Soviet sailors aboard nuclear-powered submarines where there were catastrophic failures of the reactors and, of course, the workers at Chernobyl.Diagnostic imaging involves radiation doses many magnitudes lower than the deadly levels discussed above. For example, a CT scan of the abdomen results in a dose of about 5-20 milliGrays (mGy). That is to say, .005 to .02 Gy. Such doses don’t cause acute tissue injury. Other sources of low-level ionizing radiation include radon (a decay product of naturally-occurring uranium), cosmic rays and a naturally occurring isotope of potassium, K-40.Radiobiologists believe that low level radiation is carcinogenic. This belief is based primarily on epidemiological studies of survivors of Japanese atomic bomb survivors. Extrapolating from data in these survivors, cancer rates are estimated for much tinier doses using a linear, “no threshold” model. No one knows if this model is accurate, but we do know it is the model that errs the most on the side of caution.Even using the linear no-threshold model, it is impossible to identify a cancer patient whose disease was caused by low level radiation. First, there is a latent period of 10 years or more between exposure and clinical cancer. Second, the expected incidence of excess cancers from low dose radiation is minuscule compared to the overall incidence of the same cancer in the general population. For example, the model suggests that a single exposure to 1 mGy would cause about a 0.1% (1 per 1,000) chance of developing cancer in the ensuing 20 years, while the “background” incidence of cancer is about 10% (100 per 1,000) over the same time frame.So, what are examples of mutations in humans caused by radiation exposure? Well, now you know: Skin burns, anemia, GI bleeding, coma, cancer and death.Maybe you were thinking “spider-sense” or the ability to turn into a green Hulk with superhuman strength? Sorry to disappoint you. But, hopefully, you have a better grasp of what a mutation is and what entities constitute the real biological effects of ionizing radiation.