Gene regulation in prokaryotes and eukaryotes can occur at multiple levels. In prokaryotes, the lac operon is a classic example of negative gene regulation at the transcription level. The lac operon is induced in the presence of lactose, when the lactose binds to the repressor and inactivates it, allowing transcription. In eukaryotes, gene regulation can occur through transcription factors binding promoter regions to activate transcription, or through displacement factors blocking transcription. Regulation can also occur post-transcriptionally or post-translationally.
Regulation of gene expression in prokaryotesBiswajit Sahoo
This document discusses gene regulation in prokaryotes. It begins by defining gene expression and how genes control phenotypic traits through the proteins they encode. It then describes the basic components of genes and how they can be classified based on their expression. The main part of the document focuses on different mechanisms of transcriptional regulation in prokaryotes, including different types of operons (inducible, repressible), their components (promoter, regulator, operator genes), and mechanisms of regulation like attenuation and anti-termination. The key methods of gene regulation discussed are at the level of transcription initiation through repressors and activators binding to operator sites on DNA.
This document discusses the process of translation in cells. It defines translation as the process by which the genetic information in messenger RNA (mRNA) is used to direct the synthesis of proteins. The key components involved in translation are mRNA, transfer RNA (tRNA), aminoacyl-tRNA synthetases, and ribosomes. Translation involves tRNAs carrying amino acids to the ribosome, where they are linked together into a polypeptide chain according to the codons in the mRNA.
RNA splicing is a process where introns are removed from precursor messenger RNA (pre-mRNA) and exons are joined together to produce mature mRNA. It occurs in the nucleus and is essential for eukaryotes to produce proteins. The spliceosome, a large complex of RNA and proteins, facilitates two transesterification reactions that remove introns and ligate exons. RNA splicing generates protein diversity through alternative splicing and is important for cellular functions and disease processes.
A suppressor mutation counters the effects of an original mutation by restoring the wild-type phenotype. There are two main types of suppressor mutations: intragenic mutations occur within the same gene and restore function through alternate amino acid substitutions, while intergenic mutations occur elsewhere in the genome and restore function through interacting gene products. Suppressor mutations are useful for studying protein-protein interactions and dissecting biological pathways.
Polyadenylation is the addition of a poly(A) tail to messenger RNA. The poly(A) tail consists of multiple adenosine monophosphates and plays an important role in mRNA stability, nucleocytoplasmic export, and translation. Cleavage and polyadenylation is controlled by cis elements located upstream and downstream of the polyadenylation site and involves endonuclease cleavage of the pre-mRNA followed by poly(A) polymerase addition of adenines in a template-independent manner. Alternative polyadenylation and cytoplasmic polyadenylation allow for regulation of mRNA expression through differing poly(A) tail lengths.
1) Eukaryotic gene expression is regulated at multiple levels including transcription, chromatin structure, post-transcriptional processing, and translation.
2) Regulation allows for adaptation and tissue-specific gene expression during development. Key differences from prokaryotes include the lack of operons and more complex regulation in eukaryotes.
3) Gene expression can be regulated short-term through transcriptional control, as seen in yeast galactose-utilizing genes, or long-term for development through mechanisms like chromatin remodeling.
Chloroplasts are organelles found in plant cells and algae that conduct photosynthesis. They contain their own DNA known as the chloroplast genome, which is typically 100-200kb in size and encodes genes for photosynthesis. The chloroplast genome is highly conserved and maternally inherited. It has been used for phylogenetic studies and shows potential for genetic engineering due to high transgene expression and maternal inheritance that prevents gene flow to other species.
RNA splicing is the process by which introns, or non-coding sequences, are removed from pre-messenger RNA (pre-mRNA) to produce mature mRNA that can be translated into protein. Most genes contain introns that are removed by a spliceosome, a complex of RNA and proteins, leaving just the coding exons to form mRNA. Alternative splicing allows one gene to encode multiple proteins by selecting different combinations of exons. Errors in splicing can cause diseases if they result in truncated or abnormal proteins.
Regulation of gene expression in prokaryotesBiswajit Sahoo
This document discusses gene regulation in prokaryotes. It begins by defining gene expression and how genes control phenotypic traits through the proteins they encode. It then describes the basic components of genes and how they can be classified based on their expression. The main part of the document focuses on different mechanisms of transcriptional regulation in prokaryotes, including different types of operons (inducible, repressible), their components (promoter, regulator, operator genes), and mechanisms of regulation like attenuation and anti-termination. The key methods of gene regulation discussed are at the level of transcription initiation through repressors and activators binding to operator sites on DNA.
This document discusses the process of translation in cells. It defines translation as the process by which the genetic information in messenger RNA (mRNA) is used to direct the synthesis of proteins. The key components involved in translation are mRNA, transfer RNA (tRNA), aminoacyl-tRNA synthetases, and ribosomes. Translation involves tRNAs carrying amino acids to the ribosome, where they are linked together into a polypeptide chain according to the codons in the mRNA.
RNA splicing is a process where introns are removed from precursor messenger RNA (pre-mRNA) and exons are joined together to produce mature mRNA. It occurs in the nucleus and is essential for eukaryotes to produce proteins. The spliceosome, a large complex of RNA and proteins, facilitates two transesterification reactions that remove introns and ligate exons. RNA splicing generates protein diversity through alternative splicing and is important for cellular functions and disease processes.
A suppressor mutation counters the effects of an original mutation by restoring the wild-type phenotype. There are two main types of suppressor mutations: intragenic mutations occur within the same gene and restore function through alternate amino acid substitutions, while intergenic mutations occur elsewhere in the genome and restore function through interacting gene products. Suppressor mutations are useful for studying protein-protein interactions and dissecting biological pathways.
Polyadenylation is the addition of a poly(A) tail to messenger RNA. The poly(A) tail consists of multiple adenosine monophosphates and plays an important role in mRNA stability, nucleocytoplasmic export, and translation. Cleavage and polyadenylation is controlled by cis elements located upstream and downstream of the polyadenylation site and involves endonuclease cleavage of the pre-mRNA followed by poly(A) polymerase addition of adenines in a template-independent manner. Alternative polyadenylation and cytoplasmic polyadenylation allow for regulation of mRNA expression through differing poly(A) tail lengths.
1) Eukaryotic gene expression is regulated at multiple levels including transcription, chromatin structure, post-transcriptional processing, and translation.
2) Regulation allows for adaptation and tissue-specific gene expression during development. Key differences from prokaryotes include the lack of operons and more complex regulation in eukaryotes.
3) Gene expression can be regulated short-term through transcriptional control, as seen in yeast galactose-utilizing genes, or long-term for development through mechanisms like chromatin remodeling.
Chloroplasts are organelles found in plant cells and algae that conduct photosynthesis. They contain their own DNA known as the chloroplast genome, which is typically 100-200kb in size and encodes genes for photosynthesis. The chloroplast genome is highly conserved and maternally inherited. It has been used for phylogenetic studies and shows potential for genetic engineering due to high transgene expression and maternal inheritance that prevents gene flow to other species.
RNA splicing is the process by which introns, or non-coding sequences, are removed from pre-messenger RNA (pre-mRNA) to produce mature mRNA that can be translated into protein. Most genes contain introns that are removed by a spliceosome, a complex of RNA and proteins, leaving just the coding exons to form mRNA. Alternative splicing allows one gene to encode multiple proteins by selecting different combinations of exons. Errors in splicing can cause diseases if they result in truncated or abnormal proteins.
This document discusses signal transduction in cells. It explains that membrane proteins in bacterial cells detect environmental changes and generate signals to trigger responses. In multicellular organisms, cells exchange various signals, such as plant cells responding to growth hormones and sunlight. The document then provides details on the specific and sensitive nature of signal transduction pathways, including different types of receptors and some important signal transduction pathways like G protein-coupled receptors and receptor tyrosine kinases. It also discusses two-component regulatory systems in bacteria and plants.
RNA polymerase is an essential enzyme that copies DNA to produce different types of RNA in prokaryotes and eukaryotes. In prokaryotes, a single type of RNA polymerase synthesizes mRNA, tRNA, and rRNA. Transcription in prokaryotes involves initiation at promoter sequences, elongation as the RNA polymerase moves along DNA, and termination at specific sequences. Initiation requires the RNA polymerase binding to the promoter, unwinding the DNA, and beginning RNA synthesis. Elongation continues RNA synthesis as the DNA unwinds. Termination occurs at specific sequences like palindromes that allow RNA secondary structure formation and polymerase release.
This document provides an overview of gene regulation in prokaryotes using the lac operon in E. coli as an example. It explains that genes are regulated to control which proteins are expressed at different times. The lac operon consists of structural genes that encode enzymes for lactose metabolism, as well as a regulatory gene that produces a repressor protein. In the absence of the lactose inducer, the repressor binds to the operator region and prevents transcription. When lactose is present, it binds to the repressor and causes a conformational change that prevents it from binding to the operator, allowing transcription.
This document discusses bacterial gene mapping techniques. It describes how interrupted conjugation can be used to map genes by determining the order and time at which donor alleles enter recipient bacterial cells. Recombination between donor and recipient DNA during conjugation allows for mapping analysis. Higher resolution mapping can be done by measuring recombinant frequencies between specific genes to determine smaller map distances. Interrupted conjugation experiments provide an initial rough map that is refined through additional experiments measuring recombinant frequencies between different gene combinations.
The document summarizes the lac operon which regulates lactose metabolism in E. coli bacteria. The lac operon consists of structural genes that encode enzymes for lactose breakdown. It is regulated by the lac repressor protein which binds to the operator region in the absence of lactose to prevent transcription. In the presence of lactose, the repressor detaches from the operator allowing transcription. A second control involves the catabolite activator protein (CAP) and cyclic AMP (cAMP) which activate transcription in the absence of glucose. The mechanism of induction and classification of regulatory mutants are also described.
Operon concept allows prokaryotes to coordinate gene expression. An operon contains a group of genes that are transcribed together and regulate a metabolic pathway. The lac and trp operons demonstrate induction and repression of gene expression. The lac operon induces expression of lactose-metabolizing enzymes in response to lactose. In the presence of lactose, allolactose acts as an inducer to activate the lac operon. In contrast, the trp operon represses expression of tryptophan-synthesizing enzymes in the presence of tryptophan via a repressor protein. Operons allow prokaryotes to efficiently regulate metabolic pathways in response to environmental conditions.
This document discusses gene regulation in prokaryotes. It begins by introducing gene regulation and how prokaryotes regulate gene expression mainly through transcription. It then discusses two key examples - the lac operon and tryptophan operon. For the lac operon, it describes the structure of the operon, how the lac repressor binds to DNA in the absence of lactose to prevent transcription, and how lactose or allolactose binding induces a conformational change allowing transcription. It also discusses the positive role of cAMP and CAP protein in transcriptional activation of the lac operon.
Tetrad analysis is a technique used to study genetic linkage in fungi and other lower eukaryotes. During meiosis in these organisms, four haploid spores, known as a tetrad, are produced. If spores remain in ordered linear formations, called ordered tetrads, the arrangement allows mapping of genes relative to centromeres. If spores are randomly mixed in unordered tetrads, patterns of allele segregation can determine if two genes are linked. Analysis of tetrad segregation patterns is used to calculate genetic distance between loci.
Genome organization in prokaryotes(molecular biology)IndrajaDoradla
1. In prokaryotes, the genome is located in an irregularly shaped region within the cell called the nucleoid, which is not surrounded by a membrane like the eukaryotic nucleus.
2. The prokaryotic genome is generally a circular piece of DNA that can exist in multiple copies and ranges in length but is at least a few million base pairs. It is packaged into the nucleoid through supercoiling facilitated by nucleoid-associated proteins.
3. DNA supercoiling allows for very long strands of DNA to be tightly packaged into a prokaryotic cell. This involves the introduction of plectonemic supercoils that twist the DNA into loops and wind it around nucle
RNA Polymerase
Introduction
Purification
History
PRODUCTS OF RNAP
Messenger RNA
Non-coding RNA or "RNA genes
Transfer RNA
Ribosomal RNA
Micro RNA
Catalytic RNA (Ribozyme)
prokaryotic and eukaryotic
Transcription by RNA Polymerase
TYPES OF RNA POLYMERASE
Type I
Type II
Type III
Prokaryotic Transcription Unit
EXPRESSION OF A PROKARYOTIC GENE
Prokaryotic Polycistronic Message Codes for Several Different Proteins
Eukaryotic Transcription Unit
ENHANCERS AND SILENCERS
RESULT OF THE TRANSCRIPTION CYCLE
RNAP III TRANSCRIBES HUMAN MICRORNAS
RNAP I–specific subunits promotepolymerase clustering to enhance the rRNA genetranscription cycle
RNAP II–TFIIB STRUCTURE ANDMECHANISM OF TRANSCRIPTION INITIATION
FIVE CHECKPOINTS MAINTAINING THE FIDELITY OFTRANSCRIPTION BY RNAP IN STRUCTURAL ANDENERGETIC DETAILS
Transcription in prokaryotes involves RNA polymerase producing messenger RNA transcripts of genetic material in the cytoplasm. Unlike in eukaryotes, transcription and translation can occur simultaneously. Transcription is controlled by transcription factors and involves three main steps: initiation, elongation, and termination. Initiation requires RNA polymerase binding to promoter regions with sigma factors. Elongation adds complementary bases to the DNA template. Termination can occur via intrinsic terminator sequences forming stem-loop structures or with rho-dependent termination using a rho factor protein.
The document discusses the fine structure of genes. It describes the key differences between prokaryotic and eukaryotic gene structure. Prokaryotic genes are simple and uninterrupted, while eukaryotic genes contain introns that separate coding exons. Introns have significance as they allow for alternative splicing and exon shuffling, increasing protein diversity. The document also provides history on the discovery of genes and defines key components like promoters, terminators, and regulatory elements.
RNA editing is a post-transcriptional process that makes discrete changes to RNA sequences. There are three main types of RNA editing: cytosine to uracil deamination, adenine to inosine deamination, and guide RNA-mediated insertion/deletion of uridine bases. Cytidine deamination is site-specific and involves enzymes like cytidine deaminase. Adenine deamination occurs in RNA secondary structures and involves enzymes like ADAR. Guide RNA editing involves hybridization of RNA to guide RNA, cleavage by an endonuclease, addition of uridine by TuTase, and ligation. RNA editing increases protein diversity and is essential for organelle development in eukaryotes.
The lac operon controls the breakdown of lactose in E. coli bacteria. It consists of three structural genes (lacZ, lacY, lacA) that are regulated by a single promoter and operator region. In the absence of lactose, a lac repressor binds to the operator, preventing transcription of the structural genes. When lactose is present, it binds to the repressor and causes a conformational change, releasing it from the operator and allowing transcription. Mutations in the operator, structural genes, or promoter region provided insights into the operon's control mechanism.
Identifying and studying the translational productVijay Singh
The document discusses two techniques, hybrid-release translation (HRT) and hybrid-arrest translation (HART), that are used to identify the translational product of a cloned gene by adding mRNA to a cell-free translation system and detecting radioactive proteins on a gel after translation. These techniques take advantage of purified mRNA's ability to direct protein synthesis in cell extracts containing the necessary molecules for translation. The techniques allow researchers to determine which protein is encoded by each mRNA present in the sample.
Riboswitches are RNA elements found in the 5' untranslated region of mRNA that can bind to specific metabolites and undergo a conformational change to regulate gene expression. They are classified based on the ligand they bind and their secondary structure. Examples include TPP, lysine, glycine, FMN, purine, and cobalamin riboswitches. A riboswitch has two domains - an aptamer domain that binds the ligand and an expression platform domain that can adopt two structures to control transcription or translation. Binding of a metabolite can induce formation of a terminator stem loop to terminate transcription, mask the ribosome binding site to inhibit translation initiation, or trigger self-cleavage of the mRNA.
Cell signaling involves the use of signaling molecules to transmit information between cells. These molecules can be classified as extracellular signals, like peptides, lipids, gases, and small hydrophilic molecules, or intracellular second messengers like cAMP and calcium. Extracellular signals bind to cell surface receptors and trigger intracellular pathways that regulate cell function and development. Signaling can occur through endocrine, paracrine, or autocrine pathways depending on the distance over which the signal acts. Important examples of signaling molecules discussed include peptide hormones, steroid hormones, prostaglandins, and nitric oxide. Intracellular signaling molecules like G proteins and protein kinases transmit and amplify extracellular signals within cells through the use of feedback loops and molecular switches. Breakdowns
This document discusses various classes of transcriptional regulatory elements. It begins by introducing transcriptional regulation and the basic transcriptional machinery. It then discusses the different elements that make up promoters, including the core promoter and proximal promoter elements. It also covers distal regulatory elements such as enhancers, silencers, insulators, and locus control regions. Enhancers can activate transcription from far away and silencers can repress it. Insulators protect genes from neighboring influences. Locus control regions coordinate expression of entire gene clusters.
This document discusses transposable elements (TEs), which are segments of DNA that can move within genomes. It covers their discovery by Barbara McClintock in corn in the 1940s. TEs are classified into different types based on their structure and mechanism of movement. The document also examines the mechanisms of transposition, mutagenic effects, regulation, and presence of TEs across bacteria, fungi, and eukaryotes like humans. TEs make up a large fraction of genomes and contribute to genetic variation and disease.
Gene expression involves transcription of DNA into mRNA and translation of mRNA into protein. There are two main types of genes - constitutive genes which are continually expressed, and inducible genes which are expressed only when needed. Gene expression is regulated at multiple levels, including transcription, RNA processing, translation, and post-translational modification. Key mechanisms of transcriptional control include operons in prokaryotes and the actions of transcription factors in eukaryotes.
Regulation of gene expression in prokaryotes and virusesNOOR ARSHIA
Regulation of gene expression in prokaryotes and viruses includes gene expression mechanism of prokaryotes such as lac operon ,trp operon, feedback inhibition, types of temporal response, positive and negative gene regulation. It also includes mechanisms such as reverse transcriptase in viruses.
This document discusses signal transduction in cells. It explains that membrane proteins in bacterial cells detect environmental changes and generate signals to trigger responses. In multicellular organisms, cells exchange various signals, such as plant cells responding to growth hormones and sunlight. The document then provides details on the specific and sensitive nature of signal transduction pathways, including different types of receptors and some important signal transduction pathways like G protein-coupled receptors and receptor tyrosine kinases. It also discusses two-component regulatory systems in bacteria and plants.
RNA polymerase is an essential enzyme that copies DNA to produce different types of RNA in prokaryotes and eukaryotes. In prokaryotes, a single type of RNA polymerase synthesizes mRNA, tRNA, and rRNA. Transcription in prokaryotes involves initiation at promoter sequences, elongation as the RNA polymerase moves along DNA, and termination at specific sequences. Initiation requires the RNA polymerase binding to the promoter, unwinding the DNA, and beginning RNA synthesis. Elongation continues RNA synthesis as the DNA unwinds. Termination occurs at specific sequences like palindromes that allow RNA secondary structure formation and polymerase release.
This document provides an overview of gene regulation in prokaryotes using the lac operon in E. coli as an example. It explains that genes are regulated to control which proteins are expressed at different times. The lac operon consists of structural genes that encode enzymes for lactose metabolism, as well as a regulatory gene that produces a repressor protein. In the absence of the lactose inducer, the repressor binds to the operator region and prevents transcription. When lactose is present, it binds to the repressor and causes a conformational change that prevents it from binding to the operator, allowing transcription.
This document discusses bacterial gene mapping techniques. It describes how interrupted conjugation can be used to map genes by determining the order and time at which donor alleles enter recipient bacterial cells. Recombination between donor and recipient DNA during conjugation allows for mapping analysis. Higher resolution mapping can be done by measuring recombinant frequencies between specific genes to determine smaller map distances. Interrupted conjugation experiments provide an initial rough map that is refined through additional experiments measuring recombinant frequencies between different gene combinations.
The document summarizes the lac operon which regulates lactose metabolism in E. coli bacteria. The lac operon consists of structural genes that encode enzymes for lactose breakdown. It is regulated by the lac repressor protein which binds to the operator region in the absence of lactose to prevent transcription. In the presence of lactose, the repressor detaches from the operator allowing transcription. A second control involves the catabolite activator protein (CAP) and cyclic AMP (cAMP) which activate transcription in the absence of glucose. The mechanism of induction and classification of regulatory mutants are also described.
Operon concept allows prokaryotes to coordinate gene expression. An operon contains a group of genes that are transcribed together and regulate a metabolic pathway. The lac and trp operons demonstrate induction and repression of gene expression. The lac operon induces expression of lactose-metabolizing enzymes in response to lactose. In the presence of lactose, allolactose acts as an inducer to activate the lac operon. In contrast, the trp operon represses expression of tryptophan-synthesizing enzymes in the presence of tryptophan via a repressor protein. Operons allow prokaryotes to efficiently regulate metabolic pathways in response to environmental conditions.
This document discusses gene regulation in prokaryotes. It begins by introducing gene regulation and how prokaryotes regulate gene expression mainly through transcription. It then discusses two key examples - the lac operon and tryptophan operon. For the lac operon, it describes the structure of the operon, how the lac repressor binds to DNA in the absence of lactose to prevent transcription, and how lactose or allolactose binding induces a conformational change allowing transcription. It also discusses the positive role of cAMP and CAP protein in transcriptional activation of the lac operon.
Tetrad analysis is a technique used to study genetic linkage in fungi and other lower eukaryotes. During meiosis in these organisms, four haploid spores, known as a tetrad, are produced. If spores remain in ordered linear formations, called ordered tetrads, the arrangement allows mapping of genes relative to centromeres. If spores are randomly mixed in unordered tetrads, patterns of allele segregation can determine if two genes are linked. Analysis of tetrad segregation patterns is used to calculate genetic distance between loci.
Genome organization in prokaryotes(molecular biology)IndrajaDoradla
1. In prokaryotes, the genome is located in an irregularly shaped region within the cell called the nucleoid, which is not surrounded by a membrane like the eukaryotic nucleus.
2. The prokaryotic genome is generally a circular piece of DNA that can exist in multiple copies and ranges in length but is at least a few million base pairs. It is packaged into the nucleoid through supercoiling facilitated by nucleoid-associated proteins.
3. DNA supercoiling allows for very long strands of DNA to be tightly packaged into a prokaryotic cell. This involves the introduction of plectonemic supercoils that twist the DNA into loops and wind it around nucle
RNA Polymerase
Introduction
Purification
History
PRODUCTS OF RNAP
Messenger RNA
Non-coding RNA or "RNA genes
Transfer RNA
Ribosomal RNA
Micro RNA
Catalytic RNA (Ribozyme)
prokaryotic and eukaryotic
Transcription by RNA Polymerase
TYPES OF RNA POLYMERASE
Type I
Type II
Type III
Prokaryotic Transcription Unit
EXPRESSION OF A PROKARYOTIC GENE
Prokaryotic Polycistronic Message Codes for Several Different Proteins
Eukaryotic Transcription Unit
ENHANCERS AND SILENCERS
RESULT OF THE TRANSCRIPTION CYCLE
RNAP III TRANSCRIBES HUMAN MICRORNAS
RNAP I–specific subunits promotepolymerase clustering to enhance the rRNA genetranscription cycle
RNAP II–TFIIB STRUCTURE ANDMECHANISM OF TRANSCRIPTION INITIATION
FIVE CHECKPOINTS MAINTAINING THE FIDELITY OFTRANSCRIPTION BY RNAP IN STRUCTURAL ANDENERGETIC DETAILS
Transcription in prokaryotes involves RNA polymerase producing messenger RNA transcripts of genetic material in the cytoplasm. Unlike in eukaryotes, transcription and translation can occur simultaneously. Transcription is controlled by transcription factors and involves three main steps: initiation, elongation, and termination. Initiation requires RNA polymerase binding to promoter regions with sigma factors. Elongation adds complementary bases to the DNA template. Termination can occur via intrinsic terminator sequences forming stem-loop structures or with rho-dependent termination using a rho factor protein.
The document discusses the fine structure of genes. It describes the key differences between prokaryotic and eukaryotic gene structure. Prokaryotic genes are simple and uninterrupted, while eukaryotic genes contain introns that separate coding exons. Introns have significance as they allow for alternative splicing and exon shuffling, increasing protein diversity. The document also provides history on the discovery of genes and defines key components like promoters, terminators, and regulatory elements.
RNA editing is a post-transcriptional process that makes discrete changes to RNA sequences. There are three main types of RNA editing: cytosine to uracil deamination, adenine to inosine deamination, and guide RNA-mediated insertion/deletion of uridine bases. Cytidine deamination is site-specific and involves enzymes like cytidine deaminase. Adenine deamination occurs in RNA secondary structures and involves enzymes like ADAR. Guide RNA editing involves hybridization of RNA to guide RNA, cleavage by an endonuclease, addition of uridine by TuTase, and ligation. RNA editing increases protein diversity and is essential for organelle development in eukaryotes.
The lac operon controls the breakdown of lactose in E. coli bacteria. It consists of three structural genes (lacZ, lacY, lacA) that are regulated by a single promoter and operator region. In the absence of lactose, a lac repressor binds to the operator, preventing transcription of the structural genes. When lactose is present, it binds to the repressor and causes a conformational change, releasing it from the operator and allowing transcription. Mutations in the operator, structural genes, or promoter region provided insights into the operon's control mechanism.
Identifying and studying the translational productVijay Singh
The document discusses two techniques, hybrid-release translation (HRT) and hybrid-arrest translation (HART), that are used to identify the translational product of a cloned gene by adding mRNA to a cell-free translation system and detecting radioactive proteins on a gel after translation. These techniques take advantage of purified mRNA's ability to direct protein synthesis in cell extracts containing the necessary molecules for translation. The techniques allow researchers to determine which protein is encoded by each mRNA present in the sample.
Riboswitches are RNA elements found in the 5' untranslated region of mRNA that can bind to specific metabolites and undergo a conformational change to regulate gene expression. They are classified based on the ligand they bind and their secondary structure. Examples include TPP, lysine, glycine, FMN, purine, and cobalamin riboswitches. A riboswitch has two domains - an aptamer domain that binds the ligand and an expression platform domain that can adopt two structures to control transcription or translation. Binding of a metabolite can induce formation of a terminator stem loop to terminate transcription, mask the ribosome binding site to inhibit translation initiation, or trigger self-cleavage of the mRNA.
Cell signaling involves the use of signaling molecules to transmit information between cells. These molecules can be classified as extracellular signals, like peptides, lipids, gases, and small hydrophilic molecules, or intracellular second messengers like cAMP and calcium. Extracellular signals bind to cell surface receptors and trigger intracellular pathways that regulate cell function and development. Signaling can occur through endocrine, paracrine, or autocrine pathways depending on the distance over which the signal acts. Important examples of signaling molecules discussed include peptide hormones, steroid hormones, prostaglandins, and nitric oxide. Intracellular signaling molecules like G proteins and protein kinases transmit and amplify extracellular signals within cells through the use of feedback loops and molecular switches. Breakdowns
This document discusses various classes of transcriptional regulatory elements. It begins by introducing transcriptional regulation and the basic transcriptional machinery. It then discusses the different elements that make up promoters, including the core promoter and proximal promoter elements. It also covers distal regulatory elements such as enhancers, silencers, insulators, and locus control regions. Enhancers can activate transcription from far away and silencers can repress it. Insulators protect genes from neighboring influences. Locus control regions coordinate expression of entire gene clusters.
This document discusses transposable elements (TEs), which are segments of DNA that can move within genomes. It covers their discovery by Barbara McClintock in corn in the 1940s. TEs are classified into different types based on their structure and mechanism of movement. The document also examines the mechanisms of transposition, mutagenic effects, regulation, and presence of TEs across bacteria, fungi, and eukaryotes like humans. TEs make up a large fraction of genomes and contribute to genetic variation and disease.
Gene expression involves transcription of DNA into mRNA and translation of mRNA into protein. There are two main types of genes - constitutive genes which are continually expressed, and inducible genes which are expressed only when needed. Gene expression is regulated at multiple levels, including transcription, RNA processing, translation, and post-translational modification. Key mechanisms of transcriptional control include operons in prokaryotes and the actions of transcription factors in eukaryotes.
Regulation of gene expression in prokaryotes and virusesNOOR ARSHIA
Regulation of gene expression in prokaryotes and viruses includes gene expression mechanism of prokaryotes such as lac operon ,trp operon, feedback inhibition, types of temporal response, positive and negative gene regulation. It also includes mechanisms such as reverse transcriptase in viruses.
Genome size, organization,& gene regulation in prokaryotes (lac-operon)Iqra Wazir
Genome size refers to the total amount of DNA in an organism and can vary widely between species. Prokaryotic genomes typically consist of a single circular chromosome between 0.6-10 megabases in length, and sometimes plasmids up to 1.7 megabases. Gene regulation in prokaryotes occurs at the transcriptional level through operons, which contain multiple genes regulated by a single promoter. The lac operon in E. coli contains genes to break down lactose which are regulated by a repressor protein; in the presence of lactose or its isomer allolactose, the repressor detaches from the operator and allows transcription.
This document discusses genes and gene expression. It begins by defining genes as subunits of DNA that carry the genetic blueprint and code for specific proteins. It then explains that gene expression is the process by which genes are used to direct protein assembly. There are several mechanisms that regulate gene expression, including controlling transcription, RNA processing, translation, and more. Gene expression can be regulated positively or negatively. Key examples of gene regulation discussed are the lac and tryptophan operons in prokaryotes. The document also covers gene expression in eukaryotes and some of the control points involved.
The document discusses the concept of operons in prokaryotes. It defines an operon as a coordinated group of genes that are transcribed together to regulate a metabolic pathway. The key components of an operon are structural genes, an operator, promoter and regulator gene. Operons can be regulated by repressors or activators binding to the operator, which determines if transcription occurs. Examples discussed include the lac and tryptophan operons, which are regulated by negative and positive control, respectively. Transcriptional attenuation is also described as another level of gene regulation. In conclusion, precise regulation of gene expression is essential for organisms to produce the correct phenotypes under different conditions.
The operon theory proposes that genes are organized into operons - clusters of genes under the control of a single promoter. An operon contains a promoter, operator, and multiple structural genes. The lac operon in E. coli regulates genes involved in lactose metabolism. It is negatively regulated - in the absence of lactose, a repressor binds the operator to prevent transcription, but lactose or allolactose induce transcription by binding to the repressor. The operon theory explains how bacteria regulate gene expression in response to environmental conditions.
Gene expression,Regulation of gene expression by dr.Tasnimdr Tasnim
This document discusses gene expression and its regulation. It defines gene expression as the process by which information from a gene is used to synthesize a functional product, often protein or RNA. Gene expression is regulated at multiple levels, including transcription, RNA processing, and protein utilization. The document provides details on the lac operon in E. coli as an example of prokaryotic gene regulation and compares differences in eukaryotic and prokaryotic gene expression mechanisms.
Gene regulation in prokaryotes primarily occurs at the transcriptional level through the use of regulatory proteins that activate or repress transcription. A key example is the lac operon in E. coli, which regulates the expression of genes involved in lactose metabolism. The lac operon is turned on in the presence of lactose and turned off in the presence of glucose or when lactose is not available. This is controlled by the lac repressor binding to the operator region and blocking transcription. Other examples include the trp operon and regulation by attenuation. Overall, prokaryotic gene regulation ensures the right genes are expressed at the right times through various mechanisms operating at the transcriptional and translational levels.
The document discusses genes in prokaryotes. It defines key terms like gene, prokaryotic gene, and operon. It explains that prokaryotic genes consist of a promoter region, RNA coding sequence, and terminator region. Gene expression involves transcription and translation processes that occur in the cytoplasm. Gene regulation is achieved through repressible and inducible operons like the trp and lac operons, which are controlled by repressor and activator proteins that bind to DNA in response to environmental stimuli.
Regulation of Gene Expression in ProkaryotesDoaa GadAllah
Gene expression in prokaryotes is primarily regulated at the transcription initiation step through the use of operons, which contain clusters of genes controlled by a single promoter. Operons include structural genes, operators that repressors can bind to, and promoters where RNA polymerase binds. Key examples like the lac operon are regulated by repressors that bind to the operator in the absence of an inducer, and activators like CAP that help recruit RNA polymerase to initiate transcription.
The document discusses gene regulation in prokaryotes, focusing on the lac operon in E. coli. It describes how the lac operon is regulated by a repressor protein, lactose as an inducer, and CRP/cAMP as a positive regulator. In the absence of lactose, the repressor binds to the operator region and prevents transcription. In the presence of lactose, it binds to the inducer and detaches from the operator, allowing transcription. CRP/cAMP activate transcription when glucose is low. The lac operon thus demonstrates negative and positive, inducible and repressible regulation depending on environmental conditions.
This document discusses the regulation of gene expression in prokaryotes and eukaryotes. It notes that in eukaryotes, gene expression can be regulated at the transcriptional, post-transcriptional, and translational levels. In prokaryotes, regulation primarily occurs at the transcriptional level through interactions between repressor proteins and operator sequences near promoters. A key example discussed is the lac operon in E. coli, which regulates genes for lactose metabolism through binding of the lac repressor protein to the lac operator. When lactose is present, it acts as an inducer by causing the repressor to dissociate from the operator and allowing transcription.
The document summarizes gene expression and regulation in prokaryotes. It discusses how prokaryotes transcribe genes only when needed to increase efficiency. Gene expression is regulated primarily at the transcription level through operons like the lac and trp operons. The lac operon is induced by lactose and inhibited by glucose, while the trp operon is repressed by tryptophan to control biosynthesis. Both operons use repressor proteins that bind DNA in response to metabolites to regulate transcription.
REGULATION OF
GENE EXPRESSION
IN PROKARYOTES & EUKARYOTES .
This presentation is enriched with lots of information of gene expression with many pictures so that anyone can understand gene expression easily.
Gene expression is the process by which the information encoded in a gene is used to direct the assembly of a protein molecule.
Gene expression is explored through a study of protein structure and function, transcription and translation, differentiation and stem cells.
It is the process by which information from a gene is used in the synthesis of a functional gene product.
These products are often proteins, but in non-protein coding genes such as ribosomal RNA (rRNA), transfer RNA (tRNA) or small nuclear RNA (snRNA) genes, the product is a functional RNA.
The process of gene expression is used by all known life - eukaryotes (including multicellular organisms), prokaryotes (bacteria and archaea)
Regulation of gene expression:
Regulation of gene expression includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA).
Gene regulation is essential for viruses, prokaryotes and eukaryotes as it increases the versatility and adaptability of an organism by allowing the cell to express protein when needed.
CLASSIFICATION OF GENE WITH RESPECT TO THEIR EXPRESSION:
Constitutive ( house keeping) genes:
Are expressed at a fixed rate, irrespective to the cell condition.
Their structure is simpler.
Controllable genes:
Are expressed only as needed. Their amount may increase or decrease with respect to their basal level in different condition.
Their structure is relatively complicated with some response elements.
TYPES OF REGULATION OF GENE:
positive & negative regulation.
Steps involving gene regulation of prokaryotes & eukaryotes.
Operon-structure,classification of mechanisms- lac operon,tryptophan operon ,
and many things related to gene expression.
This is a video slide so anyone can understand this topic easily by seeing pictures included in this slide.
1. Gene expression in eukaryotes involves transcription of DNA in the nucleus and translation of mRNA in the cytoplasm.
2. During transcription, RNA polymerase transcribes DNA into a primary transcript which undergoes processing including capping, splicing, and polyadenylation to produce mature mRNA.
3. The mature mRNA is exported from the nucleus to the cytoplasm where it binds to ribosomes and is translated into a polypeptide chain by the process of translation. Gene expression is regulated at transcriptional and post-transcriptional levels.
This document discusses gene expression and regulation in microbes. It explains that gene expression involves transcription of DNA into RNA, which is then translated into proteins. Some genes are constitutively expressed, while others are regulated. Regulation mechanisms control when genes are expressed and include transcription factors, riboswitches, siRNA, and operons. Operons are clusters of bacterial genes controlled by a single promoter. Types of operons include inducible operons, like the lac operon, which are turned on by substrates, and repressible operons, like the trp operon, which are turned off by products.
Regulation of gene expression and genetics.pptHanySaid33
Gene expression is regulated at multiple levels in eukaryotes and prokaryotes. In prokaryotes, gene expression is mainly controlled at the transcriptional level through the use of operons. Operons include a promoter, operator, and structural genes. In eukaryotes, gene expression is regulated at the transcriptional level as well as post-transcriptionally through RNA processing, transport, translation, and degradation. This allows for more complex regulation in eukaryotes compared to prokaryotes.
In prokaryotes, genes are regulated at the transcriptional level to control protein synthesis. There are two main types of gene regulation: negative and positive. Negative regulation occurs via a repressor protein that binds to an operator region to block transcription. Positive regulation happens when an inducer molecule activates the promoter, promoting transcription. The lac operon is an example of this, containing genes for lactose metabolism that are induced by the presence of lactose via the lac repressor protein. The operon model of gene regulation explained by Jacob and Monod helped describe this process.
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How to Fix the Import Error in the Odoo 17Celine George
An import error occurs when a program fails to import a module or library, disrupting its execution. In languages like Python, this issue arises when the specified module cannot be found or accessed, hindering the program's functionality. Resolving import errors is crucial for maintaining smooth software operation and uninterrupted development processes.
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
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International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
By Dr. Vinod Kumar Kanvaria
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Odoo provides an option for creating a module by using a single line command. By using this command the user can make a whole structure of a module. It is very easy for a beginner to make a module. There is no need to make each file manually. This slide will show how to create a module using the scaffold method.
A workshop hosted by the South African Journal of Science aimed at postgraduate students and early career researchers with little or no experience in writing and publishing journal articles.
Executive Directors Chat Leveraging AI for Diversity, Equity, and InclusionTechSoup
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This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
2. INTRODUCTION
• Gene is the basic unit of genetic information.
• Gene is made up of DNA, double helix of two inter
wound polynucleotide.
• The biological information carried by a gene is contained
in its nucleotide sequence.
• This information is in essence a set of instruction for the
synthesis of an RNA molecules that may subsequently
direct the synthesis of an enzyme or other protein
molecule.
• This sum of the total process is called “Gene Expression”
3. • The expression of gene may be assayed in term of
RNA production, protein/enzyme activity or the
specific phenotype produced.
• Eg .prokaryotes produce only those enzymes that are
needed by them at particular time.
• No cell produces all the proteins that is capable of; it
produces only that group of proteins that are required
for its efficient function.
4. Gene Expression
• Gene expression is the activation of a gene that
results in a protein
GENE REGULATION
• The mechanism by which the expression of
different genes is controlled in different tissues
and/or at different times is called Gene
Regulation, Regulation of Gene Expression or
Regulation of Gene Action.
5. Levels of Regulation of Gene Action
The expression of a gene in Prokaryotes may be
subjected to regulation at one or more of the
following levels:
Gene Amplification, Destruction or Distribution
Transcription
Post- Transcription
Translation
Post-Translation
6. i. Gene Amplification, Destruction or Distribution: Regulation at this level
determines whether a gene is present in a cell, and if present the number of copies in which
it is present. In general, those genes whose products are required in large quantities are
present in multiple copies in the genome. In addition, additional copies of some genes are
also produced by replication. These remain in extra chromosomal state; the copies are
usually produced at specific times, are used for transcription, and are subsequently
digested, this phenomenon is called Amplification.
ii. Transcription: This mechanism of gene regulation determines whether a given gene will
be transcribed or not in a given cell or at a given time. This mode of replication is
universal, so much so that ordinarily the term gene regulation implies regulation of
transcription.
iii. Post-transcriptional Regulation: Controls after transcription determines if the
mRNA produced by a gene is available for translation.
iv. Translational Regulation: Translational regulation of gene action controls if an
mRNA that is suitable for translation will be translated or not. This mode of regulation is
based on ribosome, tRNA, mRNA, regulatory proteins and regulatory RNA.
v. Post-Translational Regulation: It governs activity of the protein products of genes; it
mainly involves protein modification, protein degradation and feed-back inhibition.
7. Cont…
• Genes that encode a product required in the maintenance of basic
cellular processes or cell architecture are called housekeeping genes
or constitutive genes.
• A constructive gene is an unregulated gene, whose expression is
uninterrupted, in contrast to the regulated expression of a gene.
• The studies of bacterial genetics indicate that all genes not only
specify the structure of an enzyme but some of them also regulate
the expression of other genes.
• These genes are called regulator genes.
• This concept of gene regulation has been studied by F. Jacob and J.
Monod in 1961 in E. coli, who proposed the operon concept.
• They were awarded Nobel prize for this discovery in 1965. The
operon model was developed working with lactose region (lac
region) of the human intestine bacteria E.coli.
• The gene regulation was studied for degradation of the sugar
lactose.
8. Cont…
According to the operon concept, gene regulation
in prokaryotes and bacteriophages involves:
• Structural genes
• The operator
• The promoter
• The regulator genes
• Repressor proteins
• Co repressor
• Inducer
9. Lac Operon of E. coli
• A genetic unit that consists of one or more “structural
genes” (cistrons that code for polypeptides) and an
adjacent “operator – promoter” region that controls
the transcriptional activity is called operon.
• Operator and promoter are up stream to the structural
genes.
• Thus an operon refers to a group of closely linked
genes which act together and code for various
enzymes required for a particular biochemical
pathway.
10. Cont…
• Lac operon consists of several components:
1. Structural genes
• The lactose operon of E. coli is composed of three structural genes
z, y and a the ‘z’ gene codes for an enzyme ß-galactosidase,
which converts lactose into glucose and galactose.
• The ‘y’ gene codes for an enzyme permease, which facilitates the
entry of lactose into the cell. The ‘a’ gene specifies the enzyme
thiogalactoside transacetylase, which transfers an acetyl group
from acetyl co-A to ß-galactoside.
• Hence all the three gene products in lac operon are required for the
metabolism of lactose.
• Such genes, which are sequential and transcribed as a single m-RNA
from a single promoter are called structural genes.
• The m-RNA synthesized is the polycistronic mRNA.
• Only the last cistron has the signals for the termination of
transcription.
11. • LAC OPERON
I P O Lac Z lacY Lac A
Repressor gene Promoter-operator Β-galactose gene Permease gene Transacetylase gene
Regulatory region Structural gene
Lac operon
12. Cont…
2. The operator region
• Operator lies immediately upstream to the
structural genes between the promoter and
structural genes.
• Operator is the target site for the attachment of
repressor protein produced by the regulator gene.
• Binding of repressor with operator prevents
initiation of transcription by RNA polymerase.
• When operator is free, the RNA polymerase can
bind to the promoter to initiate the mRNA
synthesis.
13. Cont…
3. The promoter region
• The actual site of transcription initiation is known
as promoter region.
• It also lies upstream to the structural genes next to
the operator region.
• mRNA transcription by the structural gene is
catalysed by an enzyme RNA polymerase.
• This enzyme first binds to the promoter region
and then moves along the operator region and
structural genes.
14. Cont…
4. Regulator gene
• Regulator gene (i) specifies a repressor protein, which
in the absence of the inducer (lactose), bound to the
operator (o), thereby inactivating the operator and
preventing transcription of the three structural genes
by RNA polymerase.
• In the presence of an inducer (lactose), the repressor
is inactivated by interaction with the inducer.
• This allows the RNA polymerase to bind to the
promoter allowing the transcription of the adjacent
structural genes.
15. Cont…
5. Repressor
• Repressor is a protein molecule specified by
the regulator gene.
• Repressor may be in active form or inactive
form.
• In the active form, repressor binds to the
operator region and prevents transcription.
• When the repressor is in inactivate form, the
transcription takes place.
16. Cont…
6. Co repressor
• Co repressor is perhaps a product of one of the
enzymes synthesized by structural genes.
• The co repressor makes the inactive repressor
active in a repressible system after combining
with the same.
• The repressor – co repressor complex can
block the operator gene and stop protein
synthesis by structural genes.
17. Cont…
7. Inducer
• The inducer binds to the repressor making it
inactive such that it cannot bind to the operator.
• RNA polymerase path way is cleared allowing the
expression of structural genes.
• A few molecules of lactose present in the
cytoplasm of E. coli are metabolized into
allolacatose, which is an isomer of lactose.
• Such molecules that induce the expression of any
operon by binding to the repressor are called
inducers and such operons are inducible operons.
18. Regulation of Lac Operon
• In an uninduced E. coli, repressor protein binds to the operator.
• Hence, expression of structural genes is not induced. E. coli initially
contains a few molecules of ß-galactosidase enzyme.
• A few molecules of lactose slowly diffuse into cytoplasm.
• ß-galactosidase present in cytoplasm metabolises lactose into
allolactose which acts as an inducer.
• In an induced E. coli, allolactose binds to repressor protein.
• The repressor protein is detached from the operator.
• RNA polymerase allows the transcription of structural genes to
synthesize a polycistronic mRNA.
• Permease synthesized from mRNA allows the rapid uptake of
lactose.
• Large number of ß-galactosidase molecules in the cytoplasm
metabolise lactose into galactose and glucose.
19. In the "repressed or uninduced" state, the repressor bound to
the operator
20. In the "induced" state, the lac repressor can not bound to the
operator site
21. Mechanism of Gene Regulation
• The mechanism of gene regulation is of two types, viz,
(1) Negative regulation
(2) Positive regulation
• Negative Control
• In the negative regulation, absence of a product enhances the
synthesis of enzyme and presence of the product decreases the
synthesis of enzyme.
• In the lac operon of E. coli. The synthesis of protein depends
whether the operator gene is blocked or free.
• When the operator gene is free, protein synthesis by structural genes
will take place.
• On the other hand, when the operator gene is blocked, the protein
synthesis is prevented.
• Thus, the on-off of protein synthesis is governed by the free and
occupied position of the operator gene.
22. Cont…
• In negative control, regulator protein acts as a inhibitor and prevents
protein synthesis.
• In lac operon of E.coli, there is negative control of gene regulation.
• In the negative control, the regulator protein is the repressor which
inhibits protein synthesis.
• In the inducible system, the effector molecule is the inducer.
• The inducer binds with repressor and inactivates it so that it cannot
bind with operator.
• Thus, inducer permits protein synthesis by inactivating the repressor.
• In the repressible system, the effector molecule is the co repressor.
• The co repressor on binding with in-active repressor makes it active
and inhibits protein synthesis, because when repressor becomes
active it will bind with operator and stop transcription.
23. Cont…
• Positive Control
• In positive regulation, presence of a product
will enhance the synthesis of enzyme.
• In other words, in positive control the regulator
protein acts as an activator and enhances the
protein synthesis.
• The arabinose operon of E.coli is an example
of positive gene regulation.
24. Positive and negative types of control can be of
two types :
• Inducible
• Repressible
25. Negative control
1. Inducible operon
• The regulator genes of such operons produce active
repressors that bind to the operator on their own.
• When these repressors interact with molecules called
inducer (effector) they become inactive.
• The inactive repressors unable to bind operator .
• Transcription of the operon begins.
26. lac operon is a cluster of three genes coding for enzymes involved in the conversion of
disaccharide lactose to monosaccharides, glucose and galactose.
These genes do not express all the time, but only in presence of lactose
First Operon to
be discovered
was lac Operon
Jacob & Monod
27. lac operon model for gene regulation
In presence of lactose, E. coli produces -
galactosidase to break down and utilize lactose
In the absence of lactose in the medium, E. coli
shuts of the expression of this enzyme
lactose -galactosidase
galactose
glucose
28. Lactose binding changes repressor property
1. When lactose, the inducer binds to the lac repressor protein
2. The binding of lactose changes the configuration of the lac repressor protein,
inactivates.
3. The inactivated repressor protein is unable to bind to the operator region.
29. RNA polymerase binds to promoter
4. Since lactose bound repressor cannot bind to the operator region, RNA polymerase can
now bind to the promoter region and transcribes the genes
30. Transcription occurs in presence of lactose
5. RNA polymerase transcribes the three genes (Z, Y and A) of the lac operon into RNA
31. Negative control
Repressible operon
• The repressors encoded by the regulator gene is inactive and
unable to bind operator.
• The operon is normally functional or depressed, when the
repressor interacts with the effector (co repressor), it
becomes active and binds operator DNA .
• Transcription of the operon stopped.
32. Eg. Tryptophan operon
• Consist of 5 structural genes -TrpE, TrpD, TrpB, TrpC, TrpA
• When repressor encoded by gene R is inactive; it can bind the
operator sequence as a result, Trp operon transcribed.
• When Trp accumulates in cell above threshold level it interacts
with inactive repressor , transcription is prevented .
33. Positive control
1. Inducible positive control
• The activator is in an inactive state, and can not bind
DNA.
• When an inducer molecule interacts with the activator, it
becomes active and binds DNA.
• Transcription takes place.
34. Repressible positive control
• The activators is by itself is active .
• Binds to the promoter and allows transcription
• The activators become inactive when it interacts with co
repressors
• Transcription does not takes place
36. • Eukaryotes have involved a more complex system of gene regulation.
EUKARYOTIC GENE REGULATION : DIFFERENT FROM REGULATION
IN PROKARYOTES
• Eukaryotic cell contain a much greater amount of genetic information
then prokaryotic cells, and this DNA complexed with histones and other
proteins to form chromatin.
• Genetic information in eukaryotes is carried on many chromosomes,
and these chromosomes are enclosed within the double membrane
bound nucleus.
• Since the genetic information in eukaryotes is segregated from the
cytoplasm, transcription is specially and temporally separated from
translation-transcription occur in the nucleus and translation occur later
in the cytoplast. Because of this, attenuation control, a regulatory
mechanism in prokaryotes , is not possible.
• The transcripts of eukaryote genes are processed before transport to
the cytoplasm.
37. • Eukaryotes mRNA has a much longer half life than does the
prokaryotic mRNA. When prokaryotes want to stop making a
protein, they turn off transcription and the mRNA decays within
minutes.
• Because mRNA is much more stable, eukaryotes have a series of
translation control.
• More eukaryotes are multicellular with differentiated cell types.
• Gene regulation in eukaryotes
• Mechanism gene regulation is not well understood and it is more
complex
• General mode of gene regulation similar in both i.e prokaryotes
and eukaryotes
• Do not have operon
38. In Eukaryotes, gene action may be regulated at the level of :
Activation of gene structure
Transcription
Translation
Gene Replication
After Transcription
After Translation
39.
40. Regulation of transcription
• Transcription initiation begins only after binding of transcription factors
to promoter DNA.
• Which enables RNA polymerase to bind the promoter.
• It is a positive regulation
• Examples
• GRE ( gluco-corticoid response element)
• BLE ( basal level element )
• MRE ( metal response element)
• TRE ( TPA response element)
Here the binding of regulatory transcription factors to any one of the
response element is able to activate transcription initiation.
41. Negative regulation
• Eg. Gene encoding histone H2B in sea urchin; expressed only during
spermatogenesis
• Promoter has two CAAT boxes
• The CAAT binding factor must bind these two boxes for transcription to
be initiated
• But in tissues other than testis eg. embryonic tissue. These are occupied
by CAAT displacement factor
• CAAT binding factor unable to bind the CAAT boxes
• Transcription does not take place
42. The Britten-Davidson Model of Regulation
• In 1969, Roy Britten and Eric Davidson proposed a theory to explain
gene regulation in the cells of higher organisms.
• It summarizes many of the observations and assumptions made about
regulation in higher organisms.
• For example, as cells undergo differentiation, it is apparent that
previously inactive sets of gene become activated.
• Such activation is sometimes associated with external signals such as
hormonal action or embryonic inductive events.
• The essence of the model is the simultaneous regulation of batteries of
genes during development.
• Britten and Davidson proposed that repetitive sequences serve as major
control units.
43. The basic components of Britten-Davidson model
• A series of batteries of genes is activated by the presence of some signal
molecule, such as hormone.
• The hormone interacts with a sensor gene.
• This event activates a contiguous integrator gene, which produces an
activator RNA molecule.
• It is this molecule which activates genes to produce materials essential
to the cell.
• Activator RNA interacts with receptor genes (comparable to operator
regions in bacteria) to activate transcription.
• The receptor genes control the transcription of adjacent producer genes,
which are comparable to the structural genes in bacteria.
44. THE COMPONENTS OF THE BRITTEN-DAVIDSON
MODEL OF GENE REGULATION IN EUKARYOTES
45. • The model proposes that each set of producer genes in a
given battery contains a common nucleotide sequence in
its adjacent receptor gene site.
• Thus a single activator molecule may activate numerous
non contiguous producer genes, called a battery.
• The basic model may be expanded into more complex
interrelationships.
• In figure, three different sensor/integrator gene sets are
shown in relationship to six receptor/structural gene sets.
46. THE BRITTEN-DAVIDSON MODEL OF EUKARYOTIC
GENE REGULATION AND THE COMPLEX INTERACTIONS
PROPOSED IN THE MODEL
47. • Britten and Davidson revised their theoretical model in 1979
• In the modified version, repetitive sequences still serve as the focal point
of genetic regulation in eukaryotes, but play quite different role in the
process
The newer model based on following observations and assumptions:
• The mRNA nucleotide sequences found in the cytoplasm, differ in
various cell and tissue types.
• That is, transcriptional products of structural genes found in the
cytoplasm are unique when different cell types are compared.
• However, if RNA found in the nuclei of these various cell types is
examined, the uniqueness disappears.
• Thus, it may be that genetic regulation does not occur at the
transcriptional level.
.
48. • The second important observation concerns the RNA
transcripts of repetitive DNA sequences, as found in the
nuclei of different cell types.
• It is proposed that this RNA, also part of the total hnRNA,
varies quantitatively and qualitatively between specialized
cell types.
• The final portion of the revised model incorporated the recent
discovery of intervening sequences.
• These sequences found within DNA and the original RNA
transcript of structural genes are subsequently excised during
maturation of mRNA.