The Use of Non-Coding Dna in the Human Genome

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Another important function served by the non- coding regions is regulation of gene expression. One of the best examples for this phenomenon is X inactivation. Females have two copies of the X chromosome; however, the males only contain one X chromosome. If both the X chromosomes in females were indeed active, it would mean that females would have twice the amount of proteins than males. However, one of the X chromosomes in females is inactivated in a process called dosage compensation. This is achieved by a functional RNA molecule that does not code for any protein. This RNA molecule is called the Xist RNA. Xist RNA covers the entire X chromosome that needs to be inactivated. The human genome expresses many RNA molecules similar to Xist that have important cellular functions. Other such important non- coding RNAs are the tRNA and the rRNAs, both of which are extremely important for the process of translation. The tRNA molecules act as the adapters between messenger RNA and the final protein. This ensures the amino acids are added in the right order to create proper protein molecules. When two amino acids are held next to each other at the ribosome, the rRNA can carry out chemical reactions to form proteins.

In addition to the regulation brought about the regulatory RNAs like Xist, switching on a gene is dependent on a region of non- coding DNA called the promoter. There is a promoter at the beginning of every protein- coding gene. Specific transcription factors bind to the promoter sequence and recruit RNA polymerase, thereby switching on transcription. Another such regulatory DNA element is the enhancer.