Explain each of the levels of regulation of eukaryotic DNA, including those that are pre-transcriptional, post transcriptional and Post translational. Explained the role that small non-coding RNAs play and give examples.

A Non-coding RNAs is an RNA molecule which although synthesized by the process of transcription but do not undergo translation process. These non-coding RNA are called epigenetic RNAs as they control the gene expression.

These RNAs could be short and long molecules. The short molecules include Micro RNA, Piwi RNA and Short interfering RNAs. These play an important role as:

1. Micro RNA or mi RNA binds the mRNA and block the translation process by cleavage or degradation.

2. Short interfering RNAs or siRNA induce heterochromatin formation and mRNA degradation.

3. Piwi RNA or Pi RNA - interact with Piwi proteins and control Chromatin structure and transposons.