Genetics Picture

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A chromosome is a very, very long DNA molecule. Each genes consist of a little piece of such a DNA-molecule. Sometimes something goes wrong during the duplication of the chromosomes so that a part of the DNA-molecule, maybe part of a gene, is different from the original molecule. The cell with this incorrect DNA-molecule then divides, and the fault is spread further. Even gametes can have an altered DNA-molecule and then all cells in the offspring, or new organism, will have the same defect. This alteration is called a mutation. Some of such mutations don't affect the individual at all. Others may have such a drastic consequence that the individual will not be able to survive, but some mutations will give altered but healthy individuals. Example of such mutations could be the gene for non-agouti and dilution in cats. Some mutations even have a positive influence in the survival of the individual compared to other. Then this new predisposition will spread and animal and plant species have been improved through mutation. This is the basis of the theory of evolution. The natural selection will take care that only animals who are fit will survive, while unhealthy mutations will be weeded out.