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Gene expression in prokaryotes
Gene expression in prokaryotes involves the process of genetic information from DNA being made into functional gene products like proteins or RNA. Prokaryotes lack nuclei but have efficient genetic mechanisms to respond to the environment. They regulate gene expression through inducible and constitutive genes in response to substrates. A key example is the lac operon model in E. coli, which regulates 3 genes for lactose breakdown in response to lactose or IPTG through transcription control by a repressor protein.
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Gene expression in prokaryotes
- 1.
- 2. Genetic expressionis the process by which inheritable information from a gene, such as the DNA sequence, is made into a functional gene product, such as protein or RNA Non-protein coding genes (e.g. rRNA genes, tRNA genes) are transcribed, but not translated into protein
- 3. Group oforganisms lacking a cell nucleus or any other membrane-bound organelles. Differ from the eukaryotes, which have a cell nucleus Mode of division is binary fission Prokaryotes exhibit efficient genetic mechanisms to respond to environmental conditions
- 4. Rod-Shaped Bacterium, Escherichia colidividing by binary fission Rod-Shaped Bacterium, hemorrhagic E. coli, strain
- 6. * * ** * Type B
- 7. Inducible gene −Regulated by inducer/activator Constitutive gene − Not subjected to regulation
- 8. Control atthe level of transcription Induction - the production of a specific enzyme/s in response to the presence of a substrate Repression - the cessation of production of a specific enzyme/s in response to an increased level of a substrate
- 9. All ofthe genes which encode the enzymes necessary for the pathway are found next to each other on the E. coli chromosome A single mRNA carries information for multiple proteins This type of mRNA is called a polycistronic mRNA and is totally unique to prokaryotes
- 10. An operonmodel is a self-regulating series of genes found on DNA that work in concert It includes a special segment of genes that are regulators of the protein synthesis, but do not code for protein, called the promoter and operator regions Lactose (Lac), Tryptophan (Trp), L-Arabinose (Ara)
- 11. Inducible system Three genes part of an operon that code for three separate enzymes Needed for the breakdown of lactose, a simple sugar
- 13. Lac I Promoter gene Operator gene Lac ZLac Y Lac A RNA polymerase Repressor tetramer R Translation & Transcription Inactive repressor Desired product
- 14. Lac I Promoter gene Operator gene Lac ZLac Y Lac A R Translation & Transcription RNA polymerase No Gene Expressio n
- 15. Lac I Promoter gene Operator gene Lac ZLac Y Lac A mRNA R R RR Lactose absentRepressor molecules Repressor tetramer No Gene Expressio n RNA polymerase
- 16. Lac I Promoter gene Operator gene Lac ZLac Y Lac A mRNA R R RR RNA polymerase mRNA Thiogalact oside transacetyl ase Permeas e β- galactosidase Inducer Inactive repressor R Lactose/ Isopropyl Thiogalactosid e (IPTG) present
- 17. If there occursno glucose metabolism
- 18. Lac I Promoter gene Operator gene Lac ZLac Y Lac A cAMP ↑↑↑ Glucose pool gets depleted due to metabolism CAP-cAMP complex formed cAMP RNA polymerase mRNA β-galactosidase Permease Thiogalactoside transacetylase If there occurs glucose metabolism R IR I
- 19. Trp Operon Model Trp A TrpC Trp B Trp LP/O Trp E Trp D
- 21.
- 23. 1. L-arabinose operonmodel 2. Controlled by a dual positive and negative system 3. 3 structural genes: araB, araA, and araD 4. Encode the metabolic enzymes for breaking down arabinose for further metabolism via the HMP Shunt pathway