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Mutation refers to the process whereby there’s a sudden change in a given cell. This change happens spontaneously. It is the permanent change in the hereditary material of an organism’s life. A gene’s DNA sequence determines the way an organism looks like, how it behaves and the organism’s physiological make-up. Therefore, a change in the DNA sequence will result in the alteration of various aspects of an organism’s life. Mutation causes an alteration in the amino acid sequence of the protein that undergoes genetic encoding.
Very many different types of mutations are in existence, they range from chromosomal mutations to single base pair alteration of a DNA sequence. The occurrence of mutation in genes may prevent the synthesis of a particular protein or may cause a change in the protein’s level of expression if found in gene promoter areas (Leitner, 2004). If within a gene mutation occurs close to the splice regions in introns, an incorrect protein will be produced and the process of splicing will be disrupted. Most changes however are repaired quickly by the use of the DNA repair system. In cases where this repair system fails to efficiently repair the mutation that has taken place, there have been some diverse outcomes; strong and fit organisms as well as a number of genetic disorders in some cases.
It is a drug that was first introduced as a sedative that was sold to people over the counter. It is mostly used to treat myeloma. Later on pregnant women started using it to combat dizziness, insomnia, anxiety and morning sickness unaware of the effects it had on their fetuses. It is also used for the treatment of leprosy. Thalidomide intake would lead to a number of birth defects for pregnant women. The drug worked by altering new blood vessels’ process of growth and development in a developing baby, thus the birth defects.
As a drug, thalidomide is being experimented by scientists for the treatment of various serious illnesses and disorders. So far there has been a good response as regards its use in the treatment of severe cases of ulcers of the throat and of the mouth, especially in people living with AIDS and for the treatment of ulcers of the genitals and mouth among Behcet patients. The drug was approved in the treatment of multiple myeloma and erythema nodosum leprosum. However, caution has been taken to ensure it is not made available or diagnosed to women who are expectant (Williams, 2011).
Thalidomide as a drug was associated with neuropathy and teratogenicity. During its development, the drug was not thought of being able to pass through the placental barrier between the mother and her developing fetus to cause harm to the fetus. However, the drug had several effects on the developing fetus making the babies to be born with several deformities that included phocomelia, aplasia, and genital malformation among others. For instance, a baby would be born with a normal head, a normal trunk and shortened limbs or at times lack limbs. Other problems that might result include kidney abnormalities, small eyes or absence of eyes altogether, heart defects, mental retardation, facial paralysis, malformation of the ears and of the digestive tract and even gastrointestinal abnormalities.
The working of thalidomide is a process that has not fully been understood by many people. It is thought of as being the mechanism that leads to the inhibition of TNF-alpha. By enhancing the process of TNF-alpha mRNA degradation Thalidomide reduces the production of TNF-alpha. The immune system too gets affected by Thalomides’ action such that the surface adhesion molecules on epidermal cells and endothelial cells are controlled. Down regulation of key histocompatibility antigens that are also found on these cells also takes place as a result.
The end result of all this is therefore a reduction in the T-helper cells flowing, an increase in the T-suppressor cells in circulation and modification of the integrin receptors together with other receptors. Generally the mechanism of thalidomide is regarded as being linked to the properties of angiogenesis. People have therefore assumed that the drug works by reducing TNF-alpha production, modulating integrins, changing the ratio of T-cell derived cytokines, regulating the production of interleukin and angiogenesis inhibition.
As earlier mentioned, Thalidomide causes birth defects when it is used by pregnant mothers. Phocomelia which is characterized by failure of the development of long bones in the limbs as well as other deformities such as eye defects, gastrointestinal disorders, external ear malformation and malformations of the digestive tract might also occur.
Cyclopamine (Cyclops) Hedgehog signaling
Cyclopamine is a chemical belonging to the alkaloids steroidal jerveratrum and is known to occur naturally. It is known to cause serious birth defects as a teratogen. It can cause holopresencephaly, a situation in which the fetal brain is prevented from undergoing division so that there are two lobes. It works by suppressing the hedgehog gene causing this and the development of only one eye. It influences the balance between the inactive and active types of the smoothened protein leading to the inhibition of the hedgehog signaling pathway.
Birth defects, mechanism and teratogenic effects
The resulting effects of cyclopamine include craniofacial malformations, malformation of an organism’s skeletal structure and malformations of the tracheal system. Craniofacial defects are said to be as a result of the blockage of the sonic hedgehog signaling thus inhibiting normal movement of the cell in the developing embryo. Both veratrum californicum and cyclopamine-4-ene-3-one steroidal alkaloids affect the maturation of the oocyte and thus interfere with the subsequent development process of the embryo.
Currently, scientists are investigating cyclopamine for any abilities to treat multiple myeloma, rhabdomyosarcoma, medulloblastoma and basal cell carcinoma. In its mechanism, cyclopamine inhibits the hedgehog signaling pathway within cells (US National Library of Medicine, 2011). This pathway is important to the cells in that it can be used by them to be able to respond to any chemical signs from outside. Incase this pathway is interfered with; the process of embryonic development will be affected thus leading to certain deformities. It has thus been established that cyclopamine can be used to turn around certain problems and provide a treatment for a number of diseases, for example cancer.
These refer to any agents that are capable of causing disturbance to the embryonic or fetal development thus leading to birth defects in the infant. It is also possible that a teratogen can out rightly halt a given pregnancy. Teratogens can be classified into drugs, maternal infections, radiation and chemicals. Pregnant women should be careful not to use unnecessary drugs or even alcohol as these might have teratogenic effects that will interfere with the development of the embryo in their wombs. In certain instances, the medication diagnosed to a pregnant mother to treat certain complications might also be a teratogen. Care should thus be taken especially by the health specialist to provide an alternative treatment where possible. Lactating mothers might also expose their children to the dangers of teratogens through breastfeeding since some of them can be passed through breast milk. The best solution in such a case is the use of formula feeding.
Williams (2011) asserts that during gestation, teratogens are known to work with specificity by causing specific types of abnormalities during specific periods. A case in point is carbamazepine that causes neural tube defects whereas thalidomide leads to limb phocomelia in an infant. Certain drugs such as aspirin are not teratogenic when used by humans but have teratogenic effects on rats and mice. Thalidomide on the other hand has a different effect on the different species. It was found out that Thalidomide was not teratogenic in rats, no wonder its effect on humans was overlooked leading to tragic outcomes that involved human morbidity.
Only when sufficient amounts of teratogenic substances are able to reach the developing conceptus that the teratogenic effects can be felt. Factors affecting the transfer of teratogens across the placenta to the embryonic-fetal bloodstream and subsequently cause teratogenic effects include the solubility of lipids, molecular weights of the substances, the availability of a given protein carrier and polarity (Leitner, 2004). The resultant effect of a teratogen is dependent upon the stage of development within which the embryo is exposed to the substance.
Generally, in humans, teratogenicity is determined by the existence of the teratogen during organogenesis of the organ system in question, the presence of a recognizable sequence of anomalies, statistically higher level of prevalence of a certain abnormality within those exposed to the teratogen than in the controls, prior to the teratogen’s introduction within a population there’s a lower level of the anomaly’s occurrence and the facilitation of teratogenicity in experimental animals through the administration of the teratogen during organogenesis.
Cancer falls under a large group of diseases marked by the growth and proliferation of abnormal cells as a result of uncontrolled cell division. Tumors are caused by the growth of these cells into masses of tissue. Normal tissues are destroyed after they have been invaded by cancer cells. Cancer is known to be a genetic sickness caused by mutations that take place in somatic cells due to mutagens that damage the DNA. Genetic Mutations usually cause conversion of a number of normal genes that are involved in the growth, development and differentiation of the cells into oncogenes that cause cancer. Cancer can also be caused by the knocking out of suppressor genes by genetic mutations.
Cancer is caused by a multi-step process that is characterized by the interaction of genes and the environment they are exposed to. Cancer cells spread within an organism’s body through local growth of the cancerous tumor and the detachment of a number of cells which then travel via the lymphatic system and the blood to other body parts to develop other tumors there. Metastasis which is the proliferation of cancer cells may be localized in one part of the body. However, the lack of treatment might cause the cancer cells to spread further to other body parts and thus affect the entire body and lead to death.
For a cell to become cancerous, it must undergo the process of activation of five key pathways that include the growth stimulatory signals, growth inhibitory signals, apoptosis resistance, infinite proliferative capacity and angiogenic latent. Generally, cancer is an environmental disease caused by such factors as radiation, tobacco, environmental pollutants and diet accompanied by a genetic influence. These environmental factors are known to affect the genetic make up of the cells thus causing abnormalities. A given percentage of cancer is usually hereditarily inherited. The good thing however is that there is a number of treatments for this condition, for example chemotherapy, surgery and even radiotherapy.
According to www.medicalnewstoday.com (2000) depending on the type of cell a given tumor resembles, cancer can be classified into sarcoma, blastoma, carcinoma, lymphoma and germ cell tumor. Blastoma is common in small children and occurs in immature embryonic tissue. Carcinoma is linked to epithelial cells and includes prostate cancer, colon cancer, breast cancer and colon cancer. Sarcoma cancer on the other hand is associated with mesenchymal cells whereas lymphoma cancer is derived from blood forming cells known as hematopoietic cells specifically starting from the immune system. The cancer found in the ovarian and testicle regions among adults is the germ cell tumor. It also occurs in small children and is usually derived from pluripotent cells.
Hanahan (2000) explains that symptoms of this disease are dependent on the cancer type and its location in the human body. For example, in the case of colon cancer, the symptoms include blood in the stool, diarrhea and constipation. Certain kinds of cancer may completely lack symptoms while others may have symptoms that apparently can not be seen physically. Since the body energy is usurped by cancer cells to an extent that the normal hormonal function is interfered with, an individual would experience symptoms such as anemia, weight loss, fever and excessive sweating. When metastasis occurs certain newer symptoms can be observed in the region affected. Seizures, vertigo and headache might result if this cancer gets to the brain.
Though much information about genetic mutation is not yet out, basically it is known to involve the change in the genetic sequence of an organism. Various factors such as exposure to chemicals, viruses and radiations might cause genetic mutation during hyper mutation and meiosis processes. Teratogenic effects such as birth defects and other abnormalities can result due to the alteration of the DNA sequence in an individual’s body. These might be due to chemicals such as drugs that one is exposed to, for example the effect Thalidomide has on individuals. Cyclopamine too is a chemical that affects the DNA sequence in an organism thus causing certain undesirable characteristics to occur.
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