{"id":198,"date":"2023-03-09T16:29:26","date_gmt":"2023-03-09T16:29:26","guid":{"rendered":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/?post_type=chapter&p=198"},"modified":"2023-04-06T15:16:03","modified_gmt":"2023-04-06T15:16:03","slug":"prokaryotic-gene-expression","status":"publish","type":"chapter","link":"https:\/\/pressbooks.justwrite.in\/understanding-gene-regulation\/chapter\/prokaryotic-gene-expression\/","title":{"raw":"Chapter 4- How gene expression is regulated ?","rendered":"Chapter 4- How gene expression is regulated ?"},"content":{"raw":"
\r\n

Learning Objectives<\/p>\r\n\r\n<\/header>\r\n

\r\n\r\nBy the end of this chapter, readers will be able to:<\/span>\r\n
    \r\n \t
  • Define Operons<\/li>\r\n \t
  • Explain the roles of Lac I, Lac Z, and Lac Y of the lactose Operon<\/li>\r\n \t
  • Predict the effects on lactose metabolism when the concentration of lactose is changed.<\/li>\r\n \t
  • Explain about the Trp Operon<\/li>\r\n \t
  • Define attenuation<\/li>\r\n \t
  • Explain molecular mechanisms that control Eukaryotic gene regulation<\/li>\r\n \t
  • Define Epigenetics<\/li>\r\n \t
  • Discuss the role of epigenetics in gene expression and regulation<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n

    Prokaryotic Gene regulation<\/span><\/p>\r\nThe process of turning on a gene to produce RNA and protein is called\u00a0<\/span>gene expression<\/strong>. For a cell to function properly appropriate\u00a0 proteins must be synthesized at the appropriate\u00a0 time. Whether in a simple unicellular organism\u00a0 or a complex multi-cellular organism, each cell controls\u00a0 <\/span>when<\/strong>\u00a0<\/span><\/em>and\u00a0<\/span>how<\/strong><\/em>\u00a0its genes are expressed.<\/span>\r\n\r\nProkaryotic organisms are single-celled organisms that lack a defined nucleus; therefore, their DNA floats freely within the cell cytoplasm. To synthesize a protein, the processes of transcription (DNA to RNA) and translation (RNA to protein) occur almost simultaneously. The expression of a gene is a highly regulated process and ensures that a cell\u2019s resources are not wasted making proteins that the cell does not need at that time.<\/span>\r\n\r\nProkaryotic transcription and translation occur simultaneously in the cytoplasm, and regulation occurs at the transcriptional level.<\/em>\r\n

    \u00a0Regulation of Gene expression\u00a0 in Prokaryotes<\/strong><\/h1>\r\n

    Operons<\/h2>\r\nIn prokaryotes , genes with\u00a0 related functions for example\u00a0 the genes that encode the enzymes of a single biochemical pathway\u2014<\/span>\u00a0<\/span>are found next to each other on the DNA\u00a0 or clustered together and\u00a0 regulated together\u00a0 . Such gene clusters\u00a0 shares same<\/span>\u00a0<\/span>promoter and a regulatory sequence\u00a0 that controls the transcription of the entire unit.\u00a0The organization of genes in this manner is called an\u00a0<\/span>[pb_glossary id=\"946\"]OPERON.\u00a0[\/pb_glossary] <\/strong>This arrangement enables the prokaryote to rapidly adapt to changes in the environment.\r\n\r\nProkaryotic\u00a0 mRNAs are [pb_glossary id=\"944\"]Poly cistronic[\/pb_glossary]<\/strong>\u00a0 , meaning they contain the information to\u00a0<\/span>make more than one protein.<\/strong>\u00a0<\/span>The promoter has simultaneous control over the regulation of the transcription of these structural genes.\r\n\r\nThe operon includes two main components namely\r\n