Simone Lawson
Gene expression is the process by which information encoded in an organism's DNA directs the synthesis of end products, RNA or protein. The regulation of gene expression gives control over the timing, location, and amount of a given gene product present in a cell, which can have a profound effect on the cellular structure and function. Constitutive genes are genes that are continually transcribed at a rate that maintains the synthesized products at a roughly constant level. They are expressed following the interaction between a promoter and RNA polymerase and do not require a special transcription factor. Constitutive genes are found in both prokaryotes and eukaryotes, with the default state of gene expression in the latter being off rather than on.
| Characteristics | Values |
|---|---|
| Definition | Genes that are transcribed continually |
| Comparison with other genes | Opposed to facultative genes, which are only transcribed when needed |
| Interaction with promoters and RNA polymerase | Expressed following interaction at a level that doesn't vary much across cells of the same type |
| Requirement for special transcription factors | Does not require a special transcription factor |
| Experimental impact | No experimental condition has been found to greatly impact the expression level |
| Protein levels | Constitutive transcription does not imply that protein levels will continually rise |
| Expression in changing environments | Constitutive expression can provide a higher fitness benefit than responsive expression |
Explore related products
What You'll Learn
Constitutive genes are continually transcribed
Gene expression is the process by which an organism's DNA directs the synthesis of end products, such as RNA or proteins. Regulation of gene expression gives control over the timing, location, and amount of a given gene product present in a cell, which can have a profound effect on the cellular structure and function.
Housekeeping genes are a type of constitutive gene that is required to maintain basic cellular function and is typically expressed in all cell types of an organism. They are involved in providing maintenance activities for the cell, such as coding for enzymes of glycolysis and the citric acid cycle.
The regulation of gene expression is vital to allow a cell to produce the gene products it needs when required. This gives cells the flexibility to adapt to variable environments, external signals, damage, and other stimuli. Gene regulation gives the cell control over all structure and function and serves as a basis for cellular differentiation, development, morphogenesis, and the versatility and adaptability of an organism.
The expression of constitutive genes can also be influenced by environmental factors, and they may be expressed at intermediate levels. This provides an immediate benefit when the corresponding protein is needed, even though it represents a permanent cost.
The Constitution's Requirements: Setting the Standard
You may want to see also
Facultative genes are transcribed when needed
A facultative gene is a gene that is transcribed only when needed. It is the opposite of a constitutive gene, which is continually transcribed at a constant rate. The regulation of gene expression is vital as it allows a cell to produce the gene products it needs when it needs them. This gives cells the flexibility to adapt to a variable environment, external signals, damage to the cell, and other stimuli.
Facultative genes are only transcribed when they are required, and this transcription is influenced by the needs of the moment. For example, genes for proteins needed at a particular stage of the cell cycle. This allows cells to make vast quantities of some proteins and tiny quantities of others. The control of gene expression is the basis for cellular differentiation, development, morphogenesis, and the versatility and adaptability of any organism.
Gene expression is the means by which cells read out or express the genetic instructions in their genes. Because many identical RNA copies can be made from the same gene, and each RNA molecule can direct the synthesis of many identical protein molecules, cells can rapidly synthesize a large amount of protein when necessary. However, each gene can also be transcribed and translated with a different efficiency. This allows the cell to make varying quantities of different proteins.
The regulation of gene expression gives control over the timing, location, and amount of a given gene product (protein or ncRNA) present in a cell. This can have a profound effect on the cellular structure and function. Gene regulation may therefore serve as a substrate for evolutionary change.
The production of an RNA copy from a DNA strand is called transcription and is performed by RNA polymerases. These enzymes add one ribonucleotide at a time to a growing RNA strand as per the complementarity law of the nucleotide bases. This RNA is complementary to the template 3'-5' DNA strand, with the exception that thymines (T) are replaced with uracils (U) in the RNA.
Understanding Acceptance: Non-Return of Unsolicited Goods
You may want to see also
Gene expression is influenced by DNA methylation
Constitutive genes are those that are continually transcribed at a rate that maintains the synthesized products at a roughly constant level. They are expressed following the interaction between a promoter and RNA polymerase, and their expression level does not vary much across cells of the same type. Housekeeping genes, which are required to maintain basic cellular functions, are a type of constitutively expressed gene.
Gene expression is the process by which information from a gene is used to produce functional gene products, such as proteins or non-coding RNA, ultimately affecting a phenotype. Regulation of gene expression is vital as it allows cells to adapt to their environment, respond to external signals, and repair damage.
DNA methylation is essential for normal development, mediating gene expression crucial for cell differentiation and embryonic development. It facilitates genomic imprinting, where only one allele of a gene is expressed while the other is silenced through methylation, and X-chromosome inactivation, both of which are vital for normal development. DNA methylation also helps to suppress harmful repetitive element transcription and transposition, protecting the integrity of the genome.
Additionally, DNA methylation patterns can be influenced by environmental factors and early life experiences, such as social stressors or maternal psychopathology. These influences can alter methylation patterns in critical genes, potentially impacting stress responses and social behaviours. DNA methylation may also mediate some of the impacts of environmental stress on fetal development.
In summary, gene expression is influenced by DNA methylation, which acts as a regulatory mechanism to control gene expression, playing a crucial role in normal development, genome integrity, and the response to environmental factors.
The Constitutional Monarchies of Asia: A Unique Blend of East and West
You may want to see also
Explore related products
Gene expression is regulated by core promoters and enhancers
Gene expression is a highly complex process that underlies the function and fate of different cells and tissues. It involves the synthesis of a functional gene product that enables the production of end products, proteins, or non-coding RNA, ultimately affecting a phenotype. Regulation of gene expression is vital to allow a cell to produce the gene products it needs when it needs them, giving cells the flexibility to adapt to a variable environment, external signals, damage to the cell, and other stimuli.
Gene expression is regulated at multiple levels, including transcription, RNA splicing, translation, and post-translational modification of a protein. Regulation of gene expression gives control over the timing, location, and amount of a given gene product present in a cell.
Core promoters are critical elements that work in concert with other regulatory regions, including enhancers, silencers, boundary elements, and insulators. The promoter is a region of DNA sequence that provides a secure initial binding site for RNA polymerase and transcription factors. These transcription factors have specific activator or repressor sequences of corresponding nucleotides that attach to specific promoters and regulate gene expression. The promoter is recognized by RNA polymerase and a sigma factor, which are often brought to the promoter DNA by an activator protein binding nearby.
Enhancers are short regions of DNA (50-1500 base pairs) that can be bound by proteins (activators) to increase the likelihood that transcription of a particular gene will occur. Enhancers are major gene-regulatory elements that control cell-type-specific gene expression programs. They can be located up to 1 million base pairs away from the gene, upstream or downstream from the start site, and can loop through long distances to come into physical proximity with the promoters of their target genes. Enhancers, when active, are generally transcribed from both strands of DNA, producing regulatory non-coding RNA. An inactive enhancer may be bound by an inactive transcription factor, and phosphorylation of this factor may activate it. This activated transcription factor may then activate the enhancer, which can then activate a promoter to initiate transcription of messenger RNA from its target gene.
In summary, gene expression is regulated by core promoters and enhancers, which work together to control the timing, location, and amount of gene products in a cell. Core promoters provide binding sites for RNA polymerase and transcription factors, while enhancers increase the likelihood of transcription by bringing regulatory regions into proximity with the promoters of their target genes.
Constitution's Majoritarian Democracy: The Power of the People
You may want to see also
Constitutive expression provides higher fitness than responsive expression
A constitutive gene is a gene that is continually transcribed, as opposed to a facultative gene, which is only transcribed when needed. Constitutive genes are expressed following the interaction between a promoter and RNA polymerase, and so far, no experimental condition has been found to significantly impact their expression level.
Constitutive expression can provide higher fitness than responsive expression. In a rapidly changing environment, the responsive population must adapt to the new conditions, which takes time. If the environment changes faster than the population can adapt, the constitutive expression will result in higher fitness.
For example, in asymmetric environments, the constitutive population can achieve superior growth even when the response rate is ten times larger than the environmental frequency. This suggests that a fast response cannot evolve from constitutive expression via a slow response because fitness along this path would have lower than constitutive fitness.
The optimal constitutive expression level differs from the average demand for the gene product and the average optimal expression level. Depending on the shape of the growth rate function, the optimal expression level can provide intermediate fitness in all environments or maximize fitness in only one of them.
The fitness of a constitutive population is reduced by variability. Only when the population is significantly maladapted does heterogeneity provide a benefit. The benefit decreases with increasing response rates because the population will benefit more from cells that are slightly pre-adapted when the response rate is lower.
Understanding Grand Theft Auto Charges and Penalties
You may want to see also
Frequently asked questions
Constitutive genes are continually transcribed at a relatively constant rate, as opposed to facultative genes, which are only transcribed when needed.
Constitutive genes include those coding for enzymes of glycolysis and the citric acid cycle, which are required to maintain basic cellular function.
Regulated genes are only needed occasionally and are turned "on" or "off" by specific molecules, while constitutively expressed genes are always "on" and do not require external stimuli to be expressed.
Some genes are constitutively expressed to provide an immediate benefit when the protein is needed, even though this represents a permanent cost. This strategy may be advantageous in a changing environment, as adjusting protein levels can be slow.
