what is the definition of beneficial mutation and lethal mutation?
i mean in evolution and variation process
- 1 decade agoFavorite Answer
Most mutations are actually neutral (no effect). Most of our DNA is this useless baggage. Beneficial mutations may be passed down to progeny. However, natural selection should bestow a slight statistical advantage to a beneficial mutation. This does not necessarily happen in one generation, or even a dozen. Beneficial mutations actually become more likely to be favored if it has been passed to a number of individuals in a line and this group now has a better chance of passing on the trait to progeny. This might be because of increased survival or mating preferences increasing the chance of progeny. An example of a beneficial mutation might be the gene that allows us to continue to digest milk as an adult. Note that the syndrome known as "lactose intolerance" is actually a misnomer, since most people on Earth are intolerant. This mutation may have occured more than once and has spread through several populations (i.e. in Northern Europe). If a particular mutation is extremely advantageous, it will eventually filter through the entire population after many generations and become universal.
Lethal mutations are far more simple. If they affect a critical biological function, e.g. respiration, they might be expressed immediately in the form of a still birth. Also, it might result in a very unhealthy infant. Some diseases such as sickle cell anemia allow the carrier to reach adulthood and pass the trait to progeny but the trait severely shortens potential lifespan. It has been postulated that diseases such as sickle cell anemia don't die out of the genetic pool, because carrying it (though it has strongly negative consequences) protects the carrier from malaria, which in places where malaria is endemic offsets the negative to a slightly net positive. In summary, lethal mutations tend to be self-terminating, in that they do not get passed to progeny due to the early death of the carrier (or through sterility which would effectively end the line). In contrast, beneficial mutations tend to propagate and eventually infuse into the entire gene pool.
- Anonymous5 years ago
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Here is a quick overview of how evolution works. It is not a proof of evolution, which would take more space than available in this forum: --------------------------- Evolution is how changes occur in populations of existing life forms. It does not address the origin of life. The driving force behind evolution is genetic mutation. Mutations involved with evolution usually occur to genetic DNA during gamete production in sexual organisms or during cell division. They may also result from such things as trauma from chemical action or radiation. ► A mutation almost always causes death to the mutated cell, usually very quickly. Only on a rare occasion does the mutated DNA survive and rarer still is it beneficial to the host. Some mutations that survive produce a change that is neither beneficial nor harmful and the altered code passively resides in the DNA. Because some of the changes that survive long enough to be passed to the next generation are beneficial ones, some people assume (incorrectly) that all mutations are good or will "improve" the species. Yes, scientists can make certain changes in the genetic code and these can be called mutations. Some can be controlled. Although each natural mutation is random, natural selection is not. Individuals whose mutation yields an advantageous trait are more likely to reproduce, meaning that more individuals in the next generation could inherit these traits. While the changes produced in any single generation may be small, differences accumulate over generations and over time can cause substantial changes in the local population - they evolve. When an isolated population of a species has accumulated enough changes that they can no longer produce viable offspring with the rest, by definition they have become another species. In large multicellular organisms, this normally takes a great many generations. Each human has some DNA that is genetically different from the general population. Although most variations are internal and are not observed accept by specialists, you may know someone that has slightly misaligned toes, an ear shape that seems unusual or some other feature that is noticeably not in the general public. You may also notice when these traits are in several members of the same family. This is evolution in progress. In smaller, more quickly reproducing life forms the changes permeate the local population rapidly. Bacteria produce several generations in a single day and provide excellent examples of evolution. One major problem with pesticides and antibiotics is that there are vast numbers of insects and bacteria. The few that are slightly more tolerant to the chemicals may survive and quickly reproduce to pass along their genetic tolerance. .
- Anonymous5 years ago
Actually, you're exactly right. In fact, scientists do this exact thing in the lab all the time to generate mutants. If you have, say, a fly, and you want to figure out what genes are involved in growing legs, for instance, you bombard a bunch of fly with radiation and look for baby flies that don't grow legs. Then you look at their DNA to see which genes have been mutated, and you're off and researching. Now, of course, this isn't looking for beneficial mutations for the fly - the mutated flies are all pretty much screwed, one way or another, which is why this would never work for humans. The problem with looking for "beneficial" mutations is that "beneficial" depends on the evironment, and are also incredibly rare.
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- 1 decade ago
Mutations end in diseases like cancer the vast majority of the time. Lethal mutations can either be cancer or things like birth defects, mental disabilities, etc. (People born with an extra chromosome, for example).
Beneficial mutations are less likely, but they are anything that increase the fitness of the organism.
- Anonymous1 decade ago
In biology, mutations are changes to the nucleotide sequence of the genetic material of an organism. Mutations can be caused by copying errors in the genetic material during cell division, by exposure to ultraviolet or ionizing radiation, chemical mutagens, or viruses, or can be induced by the organism itself, by cellular processes such as hypermutation. In multicellular organisms with dedicated reproductive cells, mutations can be subdivided into germ line mutations, which can be passed on to descendants through the reproductive cells, and somatic mutations, which involve cells outside the dedicated reproductive group and which are not usually transmitted to descendants. If the organism can reproduce asexually through mechanisms such as cuttings or budding the distinction can become blurred. For example, plants can sometimes transmit somatic mutations to their descendants asexually or sexually where flower buds develop in somatically mutated parts of plants. A new mutation that was not inherited from either parent is called a de novo mutation. The source of the mutation is unrelated to the consequence, although the consequences are related to which cells were mutated.