Friday, March 26, 2010
Purpose to Mutation?
Mutations in the gene is essential to the creation of diversity of species and population. Jerry Coyne states on page page 128 that "Mutations are simply errors in DNA replication." Do you believe that mutations are simply errors? Could mutations occur on purpose in order to create a species that has a higher chance of survival or must all mutations be accidents/errors? Give support for your reasoning from the book/textbook/website.
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The idea of evolution is dependent on the fact that mutations are random and are only useful and reappear down an organism's line when the organism could survive and reproduce. Coyne and Campbell explain that Darwin pushed away the theory that mutations occur on purpose – this is called Lamarck’s theory of evolution.
ReplyDeleteExplained by Campbell, Lamarck’s theory of evolution is based on “use and disuse, the idea that parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate” (454). However, Darwin, as Coyne mentions, explains this not to be true in The Origin. Coyne mentions that “Natural selection… has simply changed the genetic composition of a population, increasing the population of genetic variants that enhance survival and reproduction” (117). You could read about the experiment conducted that explains natural selection yourself.
So even though we see organisms out there with great selective advantages, such as claws, hands, feet, these advantages came from mutations that were actually useful that an organism was able to pass down by surviving and reproducing. Organisms that have other mutations that weren’t so useful, like albino skin… well, their lives didn’t end very well. Evolution takes a long time to create structures that could fully perform an adequate function.
Early ancestors of the brachiosaurus didn’t grow long necks right out of nowhere to help them gain access to high trees. Instead, they had to first start off as shorter necked dinosaurs before having one that helped them get longer necks. This mutation in the gene was expressed more and more, and finally, long necks would finally be developed. Finally, the relationship between structure and function is developed.
In evolution, the mutations drive the adaptation of a species are simply random errors. Assuming that these mutations were created on purpose would be delving into the mess of a "theory" known as intelligent design.
ReplyDeleteThe illusion that organisms are purposefully adapting is caused by the proliferation of organisms with beneficial mutations, which would incur the belief that the species as a whole is purposefully attempting to change. However, there are just as many organisms that have developed harmful mutations, which would cause the organism to die before reproducing, and therefore remove the harmful mutation from the gene pool. When this process is observed, it appears that organisms are purposefully adapting because the organisms that die due to harmful mutations are ignored by the observer.
The random errors created during DNA mutation are naturally occurring processes in cell replication. When a cell replicates, it is possible for the DNA to have a mismatched set of base pairs. These mistakes are corrected by DNA polymerase during mismatch repair (Campbell 317). However, DNA polymerase lacks the ability to distinguish which base pair was the original set of base pairs, and it is therefore possible for the DNA polymerase to remove the wrong base pair, causing a mutation. Note that this is merely one of the many methods through which a mutation could occur.
The reason that this random error could have a profound effect on the organism is because the mutated DNA would transcribe different RNA which would translate into different amino acid chains. These amino acid chains would create proteins with a different structure, and therefore, through the biological theme of the relationship between structure and function, would create proteins with different functions that may or may not be beneficial to the organism.
I agree with Coyne and both Henry and Ray that mutations are simply errors in DNA replication. I think Ray pretty much said it all regarding how some mutations can come about. As Ray also mentioned not all mutations are beneficial to an organism and therefore they do not arise on purpose to create a more fit organism. When Coyne discusses natural selection with wild mice, Peromyscus polionotus, he mentions the gene Mc1r. In mice, this gene is responsible for dark/light color difference. For mice, a mutation in the Mc1r gene can cause a selective advantage for one color over another. Wild mice whose color match that of the environment are less likely to be captured by predators and can therefore survive and reproduce. In humans, however, a mutation in the Mc1r gene, "especially common in Irish populations, produces freckles and red hair" (117). This mutation provides no selective advantage (or disadvantage) for humans. Thus this mutation could not have occured to produce a more fit species.
ReplyDeleteAnother mutation that is not beneficial, but rather harmful, is the presence of cancer cells. Cancerous cells are mutations caused because a cell continues through the checkpoints in the cell cycle and continues to grow uncontrollably. As we all know, cancer is, well, bad and would provide absolutely no advantage. So far, there is no absolute cure for cancer. Treatments for cancer like radiation and chemotherapy are harmful, and they are not guarenteed to work. Very often cancer causes death, regardless of age. Many children and adolescents die from cancer without having had a chance to reproduce. Some cancers may be genetic and are passed down through families. Cancer provides a huge disadvantage, and it caused by a mutation. So how could this mutation possibly be purposeful to create a species with a better chance of survival? Mutations must be an error, a random mistake, otherwise deadly mutations like cancer or neutral ones like red hair and freckles would not arise.
I agree with the previous posts that a mutation is a change in the genetic material. I agree with Henry when he says that evolution is caused by mutation. A mutation changes the generic material of an organism, and when there is a lot of changes to the genetic material a new organism will form which is the basis of evolution. A mutation can happen to an organism that might benefit the organism. If the change in DNA helps the organism possess some natural selection quality, the organism will be able to survive better and reproduce easier. A mutation can be beneficial to the organism if the mutation helps the organism adapt better to its environment and surroundings. On page 117, Mr. Coyne states that "adaption to the environment is inevitable if a species has the right kind of genetic variation."
ReplyDeleteAn example of a mutation being beneficial to an organism can be seen with the bacteria E. coli (italics). Scientist did experiments with the bacteria and tested the bacteria cultured at lower and higher than the normal cultured temperature. What the scientist figured out from the experiments was that the bacteria being cultured at a lower temperature resulted in the bacteria being 10% more fit, and the bacteria being cultured at a higher temperature resulted in the bacteria being 20% more fit. The mutation in the genetic makeup that allowed them to handle these new temperatures resulted being beneficial to E. coli(italics). The bacteria responded better to a different environment which means that the bacteria would be able to live at places that have different temperatures and won't die there (http://www.gate.net/~rwms/EvoMutations.html).
Mutations can also be harmful to the organism like Tavor had said. "Cancer results from an accumulation of mutation" (Campbell 376). Caner develops when a cell divides uncontrollably. This dividing of the cell will result in death of the organism if not treated and stopped. In this case, the mutation doesn't help the organism survive and reproduce better but in fact does the opposite.
Mutation can be harmful to the body even if they are not cancerous. Mutations can harm the organism before they reproduce like Ray had said in his post. Mutation will help evolution only if the mutation helps the organisms survive better in its environment and reproduce better like it did with the E. coli. If the mutation harms the organism, then the mutation doesn't help evolution at all.