Distinct characteristics are not only the end result of the DNA sequence but also of the cell's internal expression system orchestrated by different proteins and RNAs present at any given time. DNA codes for many possible characteristics, but different types of RNA aided by specialized proteins, sometimes with external signals, express the necessary genes. Control of gene expression is vital to the survival of a eukaryote, such as the ability to turn genes on/off based on changes in the environment (Campbell and Reece, 2008). Only 15% of a cell's entire genome will be expressed, and in multicellular organisms the active genes will vary depending on their specialization. (Fletcher, Ivor & Winter, 2007). The amount of information encoded by genes within a cell is enormous, although some will never be expressed while others occasionally during its life cycle. For example, some genes that encode ribosomal RNA are continuously expressed because they are responsible for the formation of proteins in the cytoplasm of the cell. Specific RNA molecules and proteins are expressed in all cells at all times, and their genes are called housekeeping genes. They are responsible for the maintenance of cells and can help geneticists recognize their function (Brown, 2011). A specialized cell molecule copies a certain DNA sequence whose final product will contribute to its function. DNA is a long molecule that is usually found in a condensed state. Specialized types of proteins called histones wrap around DNA, forming nucleosomes and thus occupying a smaller volume in the nucleus. There are 2 types of nucleosomes, their importance is that they tell what will or will not be expressed. Euchromat...... middle of paper...... information needed to stimulate normal cell growth. Failure can lead to the onset of cancer. (Campbell, Reece, Urry, Cain, Wasserman, Minorsky, & Jackson, 2008)Works Cited1. Campbell NA, Reece LA, Cain ML, Wasserman SA, Minorsky PV, & Jackson RB (2008). Regulation of gene expression2. (website – Theresa Philips, Ph.D. (write science on the right) c. 2008 Nature EducationCitation: Philips, T. (2008) Regulation of transcription and gene expression in eukaryotes. Nature Education 1(1)Accessed: 02 /11/2013 www.nature.com/scitable/topicpage/regulation-of-transcription-and-gene-expression-in-1086 Hartl Daniel L. 2009 GeneticsAnalysis of Genes and GenomesAdded to library: November 18, 2013Last updated: November 18, 2013View group membership for this record View attached files View attached figureRussel Peter J. 2010 iGeneticsA Molecular Approach