Mechanisms and Effects of DNA Mutation
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Mechanisms and Effects of DNA Mutation

Whether occurring randomly or induced by mutagens, DNA mutation and recombination are at the foundation of evolution as we know it. With modern day tools Scientists have been able to determine many of the mechanisms that cause DNA mutation. In some cases these mutations can lead to serious disease or non-viable embryos.

DNA mutation and recombination can be viewed as the root of all naturally occurring species evolution. DNA mutations can lead to disease, cancer, benefits, or no phenotypic change at all. Mutations can occur for many reasons including the chemical instability of DNA base pairs within the natural cellular environment. Although the cell has evolved to recognize and restore damaged DNA, which prevents mutation, this system is not perfect and can itself produce mutation.

Point mutations are the main cause of DNA changes, generally defining the alteration of one base pair or a few neighboring base pairs. Transitions occur when one base is replaced by a base with similar chemical properties and specifies for the same amino acid. This type of synonymous mutation will have no effect on the phenotypic results and is referred to as a silent mutation. On the other hand, transversions occur when a base is replaced by another base of dissimilar chemical properties. This nonsynonymous mutation can lead to the specification of a completely different amino acid and is termed missense. Further, a nonsense mutation occurs when the codon is changed from one amino acid into a translation-termination or “stop” codon.

Another important type of mutation is referred to as indel mutations. When a nucleotide pair is either deleted or inserted, it is known as an indel mutation. The consequences of insertions and deletions of base pairs can be severe since they lead to frameshifts. This causes variation of the entire amino acid sequence downstream of the indel mutation. Frameshift mutations can lead to the complete loss of normal protein function as well as protein folding capabilities. Some severe genetic disorders are a direct effect of indel mutations.

Other forms of DNA mutation occurs when duplication of short sequences are present in the DNA. One example is Fragile X syndrome, the most common cause of inherited mental impairment. Fragile X syndrome also causes phenotypic retardation. The neurodegenerative disorder, Hunington’s disease, is another form of genetic mutation caused by sequence duplication.

In nature, mutations occur randomly and are termed spontaneous mutations. Each base has an equal probability of mutation at any given time. There are certain mutations that happen more readily than others due to the chemical properties of the nucleotides. Mutagens are also responsible for induced mutations. Mutagens can cause mispairing by mimicking a nucleotide base and incorporating itself into the DNA sequence. Another mechanism of mutagens causes the DNA base to become damaged or destroyed, preventing recognition.

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