The reason why uracil is not seen in DNA is because there are certain enzymes that break it down before it enters the DNA. The question then arises, why would an enzyme perform such a break down? The answer is simple – this is one way by which nature ensures the safety of the DNA strand. The uracil is not used directly in the DNA; it undergoes a chemical reaction and changes to another substance before being introduced into the DNA. Specifically, the uracil is converted to thymine, by a process of methylation, before it is introduced into the DNA. This kind of a conversion provides a two-pronged advantage to the DNA.
First of all, the methylation of uracil to thymine ensures that the DNA is safe. While the methylation of uracil to thymine is not the only form of methylation seen with regard to the DNA, all of these methylated materials ensure that the DNA is masked and not easily recognized by any enzymes that are specifically expert at breaking down DNA and RNA. Breaking down of a DNA strand can cause mutation. The process of methylation ensures that such radical breakdown of the DNA is avoided. Secondly, the methylation of uracil to thymine ensures that the methyl group in the uracil converted to thymine pairs only with adenine, a base substance, thereby making the process of DNA replication much more efficient.
First of all, the methylation of uracil to thymine ensures that the DNA is safe. While the methylation of uracil to thymine is not the only form of methylation seen with regard to the DNA, all of these methylated materials ensure that the DNA is masked and not easily recognized by any enzymes that are specifically expert at breaking down DNA and RNA. Breaking down of a DNA strand can cause mutation. The process of methylation ensures that such radical breakdown of the DNA is avoided. Secondly, the methylation of uracil to thymine ensures that the methyl group in the uracil converted to thymine pairs only with adenine, a base substance, thereby making the process of DNA replication much more efficient.