DNA replication is a well-evolved process that copies millions of base pairs with high fidelity during each cell division. Occasionally a wrong base or a long stretch of wrong bases may get added to the daughter strands. If the errors are left unchecked, cells might accumulate several mutations that might endanger their survival. Therefore, the copying errors are checked and repaired at three levels.
In addition to errors during DNA replication, mutations can also be caused by mobile genetic elements called transposons. They are small DNA repeat elements that can jump from one place to another on the DNA strand and disrupt the gene functions at their site of insertion. They can also cause inversions, gene duplication, or create novel genes. Transposons are of two major types: DNA transposons, which transpose directly as DNA, and RNA or retrotransposons, which transpose via an RNA intermediate. Some of these transposons result in target site duplication during their insertion at the new site on the chromosome. Such duplications at the target site can result in gene duplication, which may harm the cell function.
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