Fundamentally, the central dogma of molecular The points of control that regulate gene expression biology that dates back to Francis Crick, states that for protein-coding genes in eukaryotes are shown in genetic information is transferred through an RNA Figure 3.54. Details of each step are given below. intermediate to the amino acid sequence of proteins. 3.7.1. Transcriptional Control Thus, proteins are critical to the function of genes that Transcriptional control relates to the production of the leads to the phenotype we observe for each gene. pre-mRNA from the coding region of a protein-coding Clearly the amount of each type of protein made in a gene. Some of the factors regulating transcriptional cell determines the phenotype of the cell. The proteins control have been discussed above in . and involve the that are expressed in specific quantities and in specific transcription factors regulating the formation of the cellular locations in multicellular organisms is referred preinitiation complex (PIC) or derive from models of to understanding the expression of a gene. involving enhancer and silencer sequences in promoters We have seen that gene expression in prokaryotes is and trans-acting activator and repressor proteins that regulated primarily at the transcriptional level, and interact with these sequences. involves factors that mediate changes in mRNA levels in However there are additional aspects of cells in response to environmental and intracellular transcriptional control that also impact gene expression. factors (refer back to section 3.5.5). These include: However, we also understand that the processes of Chromatin Remodeling – transcription and translation in Eukaryotes are more In eukaryotes, the binding of DNA with histones to complex involving not just transcription and form chromatin generally represses gene expression translation, but also involving compartmentation of and is part of gene regulation. Chromatin remodeling is both transcription and translation into nuclear as well as the dynamic modification of chromatin architecture to several cytoplasmic membrane-bound compartments. allow access of condensed genomic DNA to the This establishes a basis for investigating the additional levels of complexity of these processes in Eukaryotes.
Fundamentally, the central dogma of molecular biology that dates back to Francis Crick, states that genetic information is transferred through an RNA intermediate to the amino acid sequence of proteins. Thus, proteins are critical to the function of genes that leads to the phenotype we observe for each gene. Clearly the amount of each type of protein made in a cell determines the phenotype of the cell. The proteins that are expressed in specific quantities and in specific cellular locations in multicellular organisms is referred to understanding the expression of a gene. We have seen that gene expression in prokaryotes is regulated primarily at the transcriptional level, and involves factors that mediate changes in mRNA levels in cells in response to environmental and intracellular factors (refer back to section 3.5.5). However, we also understand that the processes of transcription and translation in Eukaryotes are more complex involving not just transcription and translation, but also involving compartmentation of both transcription and translation into nuclear as well as several cytoplasmic membrane-bound compartments. This establishes a basis for investigating the additional levels of complexity of these processes in Eukaryotes. The points of control that regulate gene expression for protein-coding genes in eukaryotes are shown in Figure 3.54. Details of each step are given below. 3.7.1. Transcriptional Control Transcriptional control relates to the production of the pre-mRNA from the coding region of a protein-coding gene. Some of the factors regulating transcriptional control have been discussed above in . and involve the transcription factors regulating the formation of the preinitiation complex (PIC) or derive from models of involving enhancer and silencer sequences in promoters and trans-acting activator and repressor proteins that interact with these sequences. However there are additional aspects of transcriptional control that also impact gene expression. These include: Chromatin Remodeling – In eukaryotes, the binding of DNA with histones to form chromatin generally represses gene expression and is part of gene regulation. Chromatin remodeling is the dynamic modification of chromatin architecture to allow access of condensed genomic DNA to the