Mutations


 * Mutations **

** Mutations: Who? Where? **  ** Mutations are changes in the nucleotide sequence, which can involve large segments of DNA or a single nucleotide. They can affect any living organisms from a prokaryotic bacterium to a eukaryotic human being strand. Mutations can occur at the beginning, middle or end of a DNA strand. The DNA is located in the nucleus of the cell, which is where most mutations occur. If it is not in the nucleus, a mutation can occur in body or sperm/egg cells. ** ** If the mutation occurs in a body cell, like your heart, lungs, stomach, or skin, it will only affect that one cell. Fortunately, these mutations are not passed on to offspring. If the mutation occurs in the sperm or egg, the mutation will infect every cell in the new baby's body. This is because all of the cells in a human's body are exact copies of the original fertilized egg from which they originate. **

** Mutations usually occur in one of three ways. You can acquire the mutation from a parent, you develop the mutation from exposure to harmful chemicals or radiation, or you develop the mutation during DNA replication. One of the main causes of mutations is over exposure to ultraviolet light, nuclear radiation, and certain chemicals. These factors can damage DNA by altering nucleotide bases so they look like other nucleotide bases. When the DNA strands are separated and copied, the altered base will pair with an incorrect base and cause a mutation. In the example to the left, the G now pairs with T, insteading of forming a normal pair with C. **** DNA can also be altered by environmental agents such as nuclear radiation by breaking the bonds between oxygens and phosphate groups. If the phosphate backbone of DNA within a gene is broke, it is possible that the mutated gene will produce a protein that functions differently. Mutations result when the DNA polymerase makes a mistake, which happens about once every 100,000,000 bases. **
 * Mutations: How? **

** Mutations: Effects ** **There are three different effects that a mutation could have on an individual. There could be no effect, a positive effect, or a negative effect. If there is no effect, the mutations do not change the protein that is created or the new protein does not really change the organism in a meaningful way. If there is a positive effect, the mutation creates a protein that makes the organism more fit to survive natural selection. Finally, if there is a negative effect, the mutation creates a protein that makes the organism less fit to survive natural selection**.

** Mutations Continued: **
 * ** http://elinow-bioreviewblock1.wikispaces.com/Mutations+Continued **