Gene expression in prokaryotes and eukaryotes ppt
Presentation on theme: "Gene regulation in prokaryotes and eukaryotes"— Presentation transcript: 1 Gene regulation in prokaryotes and eukaryotes Show
2 Enzymes Speed up the chemical reactions in living organisms. 3 What are enzymes made of? 4 Some definitions: Substrate: the chemicals an enzyme acts on. 5 How do enzymes work? 2 models: lock and key induced fit
6 Metabolism Is all the chemical reactions that occur in the cell of an organism. Metabolism is made up of all the different processes an organism needs to maintain itself such as growth, energy, repair, and
excretion. These processes are a complex network of metabolic pathways which are controlled by enzymes. 7 The importance of enzymes in metabolic pathways. 8 Metabolic pathways can be: 9 Hydroxyphenylpyruvic acid 10
11 Control of gene expression in metabolic pathways 12 Gene regulation Two types of genes: 13 Gene regulation in prokaryotes 14
Structure of the operon
15 See this movie on the Lac operon in E. coli for more detail
16 See this movie on the Tryp operon in E. coli for more detail
17 http://www. sumanasinc 18 Lac Operon - induction: 19
Gene regulation in prokaryotes - summary
20 Gene regulation in eukaryotes 21 Regulatory DNA regions 22 Enhancer sequences These are non-protein-coding sections of DNA that help regulate transcription by binding proteins called transcription factors. Silencer sequences These are non-protein-coding sections of DNA that help regulate transcription by binding proteins called repressors.
23 Transcription factors 24 Transcription factors that bind to RNA polymerase 25 Role of Transcription Factors
26 Eukaryotic RNA polymerase cannot, on its own, initiate transcription. 27 Activating Transcription
28 Transcription is activated when a hairpin loop in the DNA brings the transcription factors on the enhancer sequence (activators) in contact with the transcription factors bound to the RNA polymerase at the promoter. Protein-protein interactions are crucial to eukaryotic tanscription. The RNA polymerase can only produce a mRNA molecule once the complete initiation complex is assembled.
Activators Transcription factors bound to RNA polymerase Transcription proceeds until a terminator sequence is encountered. Then transcription stops. Enhancer Promoter RNA polymerase Initiation complex 29
30 DEFECTIVE GENES Cell division is tightly controlled. If a cells DNA becomes damaged a gene (p53) within the cell causes cell division to cease until it is repaired. Other genes (proto-oncogenes) allows cell division to begin. If DNA damage is irreparable or cells get too old they self destruct, called apoptosis. If
damage occurs in either of the 2 genes mentioned above the cell will grow at an uncontrolled rate, or become effectively immortal. These cells cease to carry out normal functioning. If the damage is not too severe the cells may form a benign tumour. If many genes are affected the tumour is said to be cancerous. Lab manual page 99 How is gene expression different in prokaryotes and eukaryotes?Prokaryotic gene expression (both transcription and translation) occurs within the cytoplasm of a cell due to the lack of a defined nucleus; thus, the DNA is freely located within the cytoplasm. Eukaryotic gene expression occurs in both the nucleus (transcription) and cytoplasm (translation).
How is gene expression controlled in prokaryotes and eukaryotes?Gene expression in prokaryotes is mostly regulated at the transcriptional level (some epigenetic and post-translational regulation is also present), whereas in eukaryotic cells, gene expression is regulated at the epigenetic, transcriptional, post-transcriptional, translational, and post-translational levels.
What is gene expression in eukaryotes?Gene expression in eukaryotes is influenced by a wide variety of mechanisms including the loss, amplification, and rearrangement of genes. Genes are differentially transcribed, and the RNA transcripts are variably utilized. Multigene families regulate the amount, the diversity, and the timing of gene expression.
What is common regulation of gene expression in both prokaryotes and eukaryotes?Many genes in both prokaryotes and eukaryotes regulate their expression at the step of transcription, the DNA to RNA step in the pathway. This might make sense because both transcription and translation (the RNA to protein step in the pathway) are energetically expensive processes.
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