Whether in a simple unicellular organism or a complex multi-cellular organism, each cell controls when and how its genes are expressed. For this to occur, there must be a mechanism to control when a gene is expressed to make RNA and protein, how much of the protein is made, and when it is time to stop making that protein because it is no longer needed.
The regulation of gene expression conserves energy and space. It would require a significant amount of energy for an organism to express every gene at all times, so it is more energy efficient to turn on the genes only when they are required.
In addition, only expressing a subset of genes in each cell saves space because DNA must be unwound from its tightly coiled structure to transcribe and translate the DNA. Cells would have to be enormous if every protein were expressed in every cell all the time. The control of gene expression is extremely complex. Malfunctions in this process are detrimental to the cell and can lead to the development of many diseases, including cancer. Thanks to gene regulation, each cell type in your body has a different set of active genes—despite the fact that almost all the cells of your body contain the exact same DNA.
These different patterns of gene expression cause your various cell types to have different sets of proteins, making each cell type uniquely specialized to do its job. For example, one of the jobs of the liver is to remove toxic substances like alcohol from the bloodstream. To do this, liver cells express genes encoding subunits pieces of an enzyme called alcohol dehydrogenase. This enzyme breaks alcohol down into a non-toxic molecule. There are many other genes that are expressed differently between liver cells and neurons or any two cell types in a multicellular organism like yourself.
Many factors that can affect which genes a cell expresses. Different cell types express different sets of genes, as we saw above. However, two different cells of the same type may also have different gene expression patterns depending on their environment and internal state. Instead, they have molecular pathways that convert information—such as the binding of a chemical signal to its receptor—into a change in gene expression.
A growth factor is a chemical signal from a neighboring cell that instructs a target cell to grow and divide. This is just one example of how a cell can convert a source of information into a change in gene expression.
There are many others, and understanding the logic of gene regulation is an area of ongoing research in biology today. Growth factor signaling is complex and involves the activation of a variety of targets, including both transcription factors and non-transcription factor proteins. Alcohol dehydrogenase. Cooper, G. Regulation of transcription in eukaryotes.
In The cell: A molecular approach. Sunderland, MA: Sinauer Associates. Kimball, John W. The human and chimpanzee genomes. OpenStax College, Biology. Eukaryotic transcription gene regulation. Regulation of gene expression. Phillips, T. However, two different cells of the same type may also have different gene expression patterns depending on their environment and internal state. Instead, they have molecular pathways that convert information—such as the binding of a chemical signal to its receptor—into a change in gene expression.
A growth factor is a chemical signal from a neighboring cell that instructs a target cell to grow and divide. This is just one example of how a cell can convert a source of information into a change in gene expression.
There are many others, and understanding the logic of gene regulation is an area of ongoing research in biology today. Growth factor signaling is complex and involves the activation of a variety of targets, including both transcription factors and non-transcription factor proteins. Alcohol dehydrogenase. Cooper, G. Regulation of transcription in eukaryotes. In The cell: A molecular approach.
Sunderland, MA: Sinauer Associates. Kimball, John W. The human and chimpanzee genomes. OpenStax College, Biology. Eukaryotic transcription gene regulation. Regulation of gene expression. Phillips, T. Regulation of transcription and gene expression in eukaryotes. Nature Education , 1 1 , Purves, W. However, it is usually absent from or at very low levels in most somatic cells.
In normal cells, the telomere is shortened when a linear chromosome is duplicated. Activation of telomerase is one of the processes that let cancer cells become indefinite. Telomerase allows each offspring to avoid losing a bit of DNA, making the normal cells divide without limitation and become abnormal cells, and the unbounded cell growth is a characteristic of cancer.
Epigenetics is the study of heritable phenotype changes that do not involve alterations in the DNA sequence, meaning a change in phenotype without a change in genotype. The term also refers to the functionally associated changes to the genome that do not encompass a change in the nucleotide sequence.
At present, DNA methylation, histone modification, and noncoding RNA ncRNA -associated gene silencing are major functions for involving in the initiation and support of epigenetic changes. It often indicates changes that affect gene activity and expression and shows phenotypic changes which can be transferred to the offspring. Epigenetic changes can be influenced by several factors including the age, environment, lifestyle, and disease; it is traditionally considered to be regular and natural.
The process of cellular differentiation is an example of an epigenetic change in eukaryotic biology. In , Griffith and Mahler first suggested that DNA methylation might play a crucial role in long-term memory function. DNA methylation has currently become one of the most extensively studied and well-characterized epigenetic modifications. The other main modifications include chromatin remodeling, histone modifications, and noncoding RNA mechanisms.
The new findings about epigenetics are the correlation between epigenetic changes and diseases such as cancers, mental retardation, immune disorders, neuropsychiatric disorders, and pediatric disorders. Not only the environment but also individual lifestyles can directly interact with the genome to affect epigenetic changes.
The prenatal and early postnatal environmental factors can influence the adult risk for the incidence of various chronic diseases and behavioral disorders in human epidemiology studies. It is known that the children have elevated rates of coronary heart disease and obesity after their mothers are exposed to famine during early pregnancy compared with those who are not exposed. Similarly, the adults who were prenatally exposed to famine have also been reported to have significantly higher incidence of schizophrenia.
Fortunately, maternal ingestion of vitamin D is capable to adjust DNA methylation that impacts placenta function. Epigenetics are considered to be dynamic and changeable by the influence of lifestyle options and environmental factors, though our epigenetic marks are more stable during adulthood. Epigenetic effects gradually occur both in the womb and the full course of a human life span, and epigenetic changes could be reversed.
Epigenetics have shown that different lifestyle options and environmental exposures can change DNA marks and play a vital role in the determination of health outcomes. The environment can dominantly influence the epigenetic tags and disease susceptibility.
Fortunately, vitamin B groups potentially protect humans from harmful epigenetic effects of pollution and against the other harmful effects on the body. It is known that chronic pancreatitis causes a high risk of inflammation-associated progression to pancreatic cancer. The difficulty in rapidly diagnosing the disease is closely associated with its high mortality rate.
Previous studies have demonstrated that cell-free DNA methylation from inflammatory diseases or cancer is variable, thereby opening a new era in developing biomarkers for the early diagnosis of diseases.
Hence, early diagnosis for pancreatic cancer becomes crucial and facilitates the related studies into the epigenetic profiles [ 1 ]. Natale et al. Early diagnosis potentially makes it possible for the prediction of prognosis, the monitoring of tumor progression, and the development of effectively therapeutic strategies and provides precision medicine for patients suffering from a pancreatic disease [ 1 ]. The early-life environment including air quality is known to be critical for fetal programming.
The air pollution exposure to mothers during pregnancy may adversely influence newborn outcomes such as baby birth weight, preternatural birth, and preterm birth. Therefore, it is needed to understand both air pollution-induced early health effects and its later-life consequences.
Saenen et al. They reported that nitrosative stress and epigenetic alterations in the placenta may result from the prenatal exposure to air pollution [ 2 ]. It is crucial to realize the clinical consequences of early-life epigenetic changes in the follow-up of child or birth cohort study.
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