37. Gene and regulation of the gene activity. Operon and its functions. Flashcards
Gene is a part of the DNA molecule occupying a certain chromosome locus that induces functional units, mutation units and recombination units.
It’s the basic unit of heredity, a linear sequence of nucleotides of DNA that provides the coded instructions for synthesis of RNA, which when translated into proteins, leads to the expression of hereditary character.
Gene is a part of the DNA molecule occupying a certain chromosome locus that induces functional units, mutation units and recombination units.
It’s the basic unit of heredity, a linear sequence of nucleotides of DNA that provides the coded instructions for synthesis of RNA, which when translated into proteins, leads to the expression of hereditary character.
Control of gene expression in prokaryotes:
- transcription and translation coupled .’. gene regulation is coupled through transcription
Control of gene expression in prokaryotes:
- transcription and translation coupled .’. gene regulation is coupled through transcription
Definition: Operon is a set of genes that are adjacent to one another in the genome and are coordinately controlled, all of them are turned on or off. When RNA polymerase transcribes the operon, a polycistronic mRNA is produced, that codes for all the proteins of the operon
Definition: Operon is a set of genes that are adjacent to one another in the genome and are coordinately controlled, all of them are turned on or off. When RNA polymerase transcribes the operon, a polycistronic mRNA is produced, that codes for all the proteins of the operon
Operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a promotor. Operon control can be positive or negative, by either induction or repression that enables organisms to regulate the expression of various genes depending on environmental conditions.
Operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a promotor. Operon control can be positive or negative, by either induction or repression that enables organisms to regulate the expression of various genes depending on environmental conditions.
Operons contain promotor regions where proteins bind and facilitate or inhibit the binding of RNA polymerase
Operons contain promotor regions where proteins bind and facilitate or inhibit the binding of RNA polymerase
Prokaryotes - regulation occurs mainly at the transcriptional level through operons
Prokaryotes - regulation occurs mainly at the transcriptional level through operons
Eukaryotes - regulation may occur by modification of DNA or at the level of transcription and translation
- genes may be deleted or amplified, rearranged or methylated
- histones may non-specifically repress transcription of genes. Inducers cause genes to be activated
- synthesis of some proteins can also be regulated at the level of translation during initiation and elongation
Eukaryotes - regulation may occur by modification of DNA or at the level of transcription and translation
- genes may be deleted or amplified, rearranged or methylated
- histones may non-specifically repress transcription of genes. Inducers cause genes to be activated
- synthesis of some proteins can also be regulated at the level of translation during initiation and elongation
Inducible (lac operon):
- for metabolic pathways that are usually “off” When lactose is absent:
- repressor protein attaches to operator
- RNA polymerase cannot transcribe structural genes lac 2, lac Y + lac A to an enzyme that digests lactose, because cannot attach to promotor
- Normal state
Inducible (lac operon):
- for metabolic pathways that are usually “off” When lactose is absent:
- repressor protein attaches to operator
- RNA polymerase cannot transcribe structural genes lac 2, lac Y + lac A to an enzyme that digests lactose, because cannot attach to promotor
- Normal state
When lactose is present:
- inducer binds to repressor on its allolactose site
- repressor cannot bind to promotors
- lactose digested
When lactose is present:
- inducer binds to repressor on its allolactose site
- repressor cannot bind to promotors
- lactose digested
Repressible:
- for metabolic pathways that are usually “on”
- when tryptophan (trp) level is low
- repressor protein is unable to attach to the promotor
- RNA polymerase transcribes the structural genes (Trp A, B, C, D, E) needed to synthesise trp
- constant low level of production of trip
Repressible:
- for metabolic pathways that are usually “on”
- when tryptophan (trp) level is low
- repressor protein is unable to attach to the promotor
- RNA polymerase transcribes the structural genes (Trp A, B, C, D, E) needed to synthesise trp
- constant low level of production of trip
When Trp is present
- Trp binds to repressor
- shape of repressor changes, attaches to operator
- RNA polymerase cannot transcribe structural genes needed to synthesise trp
- continue until cytosol levels of trip decline
When Trp is present
- Trp binds to repressor
- shape of repressor changes, attaches to operator
- RNA polymerase cannot transcribe structural genes needed to synthesise trp
- continue until cytosol levels of trip decline
Lac operon - up regulation
- to increase the rate of transcription of an operon When lactose is present and glucose is low
- body prefers glucose to lactose
- low glucose means amount of CAMP is high
- CAMP binds to cap protein activating it, CAMP/ Cap complex helps RNA polymerase to promotor - increase rate of transcription
Lac operon - up regulation
- to increase the rate of transcription of an operon When lactose is present and glucose is low
- body prefers glucose to lactose
- low glucose means amount of CAMP is high
- CAMP binds to cap protein activating it, CAMP/ Cap complex helps RNA polymerase to promotor - increase rate of transcription
When glucose + lactose both present
- normal glucose level means amount of CAMP is low
- no camp for cap
- cap inactive
- little lactose gene transcription occurs
When glucose + lactose both present
- normal glucose level means amount of CAMP is low
- no camp for cap
- cap inactive
- little lactose gene transcription occurs
Control of gene expression in eukaryotes:
- expression of genes into proteins can be controlled at different locations
- synthesis of proteins is controlled right from chromatin stage
Control of gene expression in eukaryotes:
- expression of genes into proteins can be controlled at different locations
- synthesis of proteins is controlled right from chromatin stage
Regulation in the chromatin stage:
- mechanisms which affect the chromatin structure and hence the expression of the genes are:
- histone modifications
- methylation of DNA
Regulation in the chromatin stage:
- mechanisms which affect the chromatin structure and hence the expression of the genes are:
- histone modifications
- methylation of DNA
