Regulation of gene expression in Eukaryotic cells
Due to the complexity involved in eukaryotic cells, the processes of regulating gene expression may as well be complicated. As a result the process involves many different levels to effectively control the hundreds of cells in a eukaryotic organism. Regulation of gene expression in eukaryotes takes place not only during the process of transcription but also during protein synthesis since the protein produced as the final product performs the function that the expressed gene specifies.
Expression of genes may be regulated during transcription (transcriptional regulation) or after transcription has already occurred (post-transcriptional regulation). Transcriptional regulation involves factors that prevent the coding of a DNA sequence into a messenger RNA or basically the mechanisms control the amount of RNA produced.
The major mechanism used to regulate the transcription process is the control of the binding between the RNA polymerase and the DNA since this bond forms the bridge through which he codes would be sent. Binding of non coding molecules known as repressors to the protein that triggers the binding also controls transcription by altering the structure of the protein to either enhance or prevent the binding process. Certain molecules such as activators and enhancers may also be used in favor of transcription by promoting the bonding of polymerase and DNA to be transcribed. Post transcriptional regulation involves regulating the amount of the mRNA to be translated.
This is done by splicing or capping of the some of the mRNA molecules. Gene regulation in eukaryotes may as well be translational or post translational. Translational regulatory mechanisms work by regulating the amount of mRNA to be processed into proteins. This is done by regulating the transport of these molecules from the nucleus to the cytoplasm from which translation takes place. Factors such as temperature changes have also been confirmed to alter the structures of the binding molecules resulting to antisense binding of the mRNA molecule to chromosomes. After translation has occurred, post translational mechanisms may occur in the cell such as degradation of the protein molecule formed or the proteins may be modified through addition of glucose, acetyl or fatty acid molecules (King, M.W. 2011, p. 1).
Gene expression alterations and cancer
Alterations in gene expression occur through many mechanisms which basically involves changing of the base sequences in the genetic material. One of the major mechanism through which gene expression is altered is addition where a base pair is added to the normal sequence hence changing the specificity of the protein that the code specifies. Addition results to production of a nonsense sequence which does not specify any of the proteins.
Deletion of a base pair(s) is another common mechanism where one or more base pairs are deleted from the normal three base sequences. Similar to addition, deletion results to production of nonsense codes (base sequences which do not specify production of any protein). Another mechanism is substitution which involves replacing a specific base pair with a different one. As a result, the sequence specific for a given protein is changed to another code which in rare cases specifies the same protein or specifies the production of a different protein. Another mechanism is inversion where a base pair turns upside down from its normal position.
This may as well lead to formation of a nonsense sequence. Continued accumulation of these genetic alterations which result to altered expression of genes is what causes cancer development. These alterations are known to cause DNA mutations which in turn disrupt the processes that regulate cell proliferation and cell death. The result is uncontrolled division of cells which accumulate and develop into tumors.
How cancer is formed
The formation of cancer involves several steps. Due to unregulated division of body cells over many successive generations, the cells develop abnormally over and over. With time, they gain new potential to perform certain functions such as release of growth factors and different types of enzymes. As the cells continue growing, they affect their neighboring cells which eventually cause complete or reduced dysfunction of the affected organs. This is usually followed by a critical step where new blood vessels are developed. Through these vessels, nutrient supply to the cancer cells is facilitated as well easy movement of the cancer cells throughout the rest of the body.
The next stage involves development of the solid tumor itself. Although all cancers do not have these steps when developing, these are the general steps that occur in many cases of cancer development. At each of these steps, the cancer cells may progress or may even lessen. However, for cancer to develop completely, mutations must occur and the abnormal cells be alive and continuously dividing as well. Activation of mechanisms to repair DNA can prevent or terminate the development of cancer cells (Ginger, 2008, p. 1).
Genetic changes in cancer cells
The genetic makeup of cancer cells is different from that of normal cells. Some of the genetic changes that occur include presence of one or more copies of chromosomes resulting to alteration in the normal chromosome number. Other genetic changes in cancer cells may even damage the chromosomes. Another very common genetic change in cancer cells is the division of the tumor cells where they divide moving towards the poles opposed to normal cells which divide in opposite directions.
This often results to fusion of three poles into a single daughter cell forming a daughter cell with extra chromosome(s). Continued division of such cells eventually results to production of chromosome sets that are completely different from the normal one. When the cancer cells accumulate during its development, many cells that are genetically different gets mixed up within the tumor and this results to a lower immune response of the patient to chemotherapy and other treatments as well.
These changes are known to affect the behavior of cells since the genes are the controlling factor of cell behavior. Many of the regulatory mechanisms in the body are controlled by genes such as homeostasis and cell division. As we all know, these processes are very vital in the body. Genetic changes in cancer cells may alter the normal pathways that signal, initiate or even regulate these body processes.
Other cancer cells may prevent the cell cycling pathway since all the components that control and regulate this pathway are altered by mutations resulting from cancer cells. Interference of these very vital processes may endanger the body especially when homeostasis is altered because control of sugar and water levels in the body will be interfered with resulting to certain conditions such as diabetes. Cancer cells also prevent apoptosis which involves programmed killing of cells without affecting other cells to regulate their presence in the body for normal functioning (Hoffman, 2010, p. 1).
Reference List
Ginger, L. (2008). Four Major Phases of Tumor Formation. Web.
Hoffman, E. (2010). Genetic Changes in Cancer. Web.
King, M.W. (2011). Gene Control in Eukaryotes. Web.
Milestones in Discovery. (1995). Gene Alterations and Cancer. Web.