GENE EXPRESSION
Every gene in a normally operating cell performs its own strictly defined function. For example, it can be responsible for protein production, or mRNA, or for interaction with other regulatory proteins. In this case they speak of a normal expression of this gene in the cell (from the Lat. expressus - expressive, explicit). However, if the amount of the product of a certain gene (for example, some protein) decreases or increases, then they speak of modulation (change) of this gene expression. Modulation of gene expression can be performed on various levels, transcriptional or translational one. The effect of directive decreasing of the expression of certain genes by small RNAs on the transcriptional level is called RNA-interference.
Expression of eukaryotic genes is a complex and multistage process of realization of genetic information, encoded in DNA. It includes such stages as transcription, mRNA processing, translation, post-translational modification of the protein.