Regulation of Gene Expression

Gene expression can be regulated at the stage of transcription, RNA processing (post- transcriptional changes), and translation. In prokaryotes, the on–off of transcription serves as the main regulatory control of the gene expression whereas, in eukaryotes, more complex regulatory mechanism of transcription takes place. In addition, RNA splicing also plays a major role in the regulation of gene expression. The primary transcript of DNA has complementary sequences of both exons and introns, and is termed heterogeneous RNA (HnRNA). The HnRNA is spliced by the removal of introns and the ligation of exons. The regulation of gene expression in both prokaryotes and eukaryotes is important, as it determines whether a particular protein should be synthesized, and in what quantity. The cells of a multicellular organism are genetically homogeneous, but structurally and functionally heterogeneous, owing to the differential expression of genes. Many of these differences in gene expression arise during development, and are subsequently retained through mitosis. Stable alterations of this type are termed epigenetic. These alterations are heritable in the short term, but do not involve mutations of the DNA itself. The main molecular mechanisms that mediate epigenetic phenomena are DNA methylation and histone modification(s). Keywords: Alternate splicing; Alzheimer's disease; Attenuation; Bromodomain; CAAT box; Chromodomain; Coffin–Lowry syndrome; Cyclic AMP receptor protein (CRP or CAP); Epigenetics; Epigenotype; Epigenetic regulation; Exon; Gratuitous inducer; Intron or intervening sequence; Inducer; Induction; Lariat; Leader sequence; Myoblast; Operator; Polyadenylation; Polycistronic mRNA; Promoter; Regulatory gene; Repression; Rett syndrome; Riboswitch; Ribozyme; RITS (RNA-induced transcriptional silencing); SnRNAs (small nuclear RNAs); SnRNPs; Splicing; TATA box; Telomerase; Telomere; Totipotent; Tropomyosin; Upstream