The Different Characteristics of the Specie - Case Study Example

AR Genetic Problems 11/25 Genetic Problems Overview of Abnormalities In the world today many species have been recognized and each of these species have a distinct set of characteristics. Each specie has different DNA(deoxyribo-nucleic acid) molecules which encode the genes and different genes determine the different characteristics of the specie. Every cell of the living organism contains chromosomes in the nucleus which present with DNA molecules. The genes encoded in the DNA are transmitted from parents to the offspring by reproduction which means that the basic elements of heredity are genes. The study of genes or the elements of heredity is called genetics. Sometimes errors can occur in the transmission of genetic material from parents to offspring or in the structure of the genetic material causing serious disorders in human beings. Structural chromosomal abnormalities arise when different enzymes are not able to repair several breaks in the pattern of chromosomes or even if they are able to do so these repairs are not specific enough to avoid the abnormality. These can be caused by chemicals, radiations, viruses, or any other type of abnormal event. These structural abnormalities are classified into four main classes respectively. These are Deletions, Translocations, Inversions and Ring Chromosome (Langman & Sadler 2006; Robbins et al 2005). Other names of deletion are gene deletion and deficiency mutation. Deletion is that type of genetic abnormality in which a sequence of DNA is absent in the chromosome or a part of chromosome is absent. It results in the loss of the genetic material from the chromosome. Translocation is also genetic aberration which occurs due to the rearrangement of the different parts of chromosome with nonhomologous chromosomes. Translocations are of two types that are reciprocal translocations and Robertsonian translocations. Reciprocal translocation is the translocation of genetic material between nonhomologous chromosome. These type of chromosomal translocations are harmless. When the two acrocentric chromosome fuse near the centromere resulting in loss of the short arm, this type of translocation is called Robertsonian translocation. In Robertsonian translocation the resulting karyotype in humans is 45 chromosomes. Inversion is that type of chromosomal abnormality in which a part of chromosome is split and introduced back to the same chromosome. Inversion is basically the aberration in a single chromosome itself and is not associated to other homologous or nonhomologous chromosome. Inversions are of two types paracentric and pericentric. Inversions which do not involve centromere are called paracentric inversions. Pericentric inversions are of that type which incorporate the centromere (Langman & Sadler 2006). Turners Syndrome Ring Chromosome is a form of deletion in which ends of chromosomes fuse together to make it up for the damaged segments. Usually it is seen that no genetic material is lost in the formation of a ring chromosome but in some cases this material is lost and an abnormality occurs. Turners Syndrome is an example of chromosomal ring formation. Turners Syndrome is usually seen in women and results from defects in the X chromosome. The deletions of long or short arms of a chromosome can cause the ring structure to be formed. These patients show signs of edema in infancy with resultant cystic hygroma in some patients. It is also a leading cause of heart disease in these patients which particularly occurs because of coartcation of aorta or defects in the aortic valve. Patients suffering from Turners Syndrome normally are not able to develop sexual characteristics even at the age of puberty. Amenorrhea is also seen in these patients along with hypothyroidism. As the X chromosome is absent in these individuals it is seen that a great number of oocytes are lost by these patient at the age of puberty because of which they are not able develop the sexual characteristics. Other signs of Turners Syndrome seen in patient are infertilitization, pigmented nevi, short stature, cubitis valgus and streak ovaries (Robbins et al 2005). Diabetes Mellitus Diabetes mellitus is a disease characterized by greater glucose levels in the body because of the body’s resistance to insulin or lack of insulin in the body. Type I Diabetes can be easily detected in the preliminary stages because the symptoms of such a disease are acute. However the signs and symptoms of type II diabetes may be difficult to interpret. In diabetes mellitus it can be generally seen that a person suffers from polyuria, polydipsia and polyphagia. Moreover the person also gets fatigued easily, suffers from infections, has a reduced wound healing time and loss of weight occurs in the individual. The reduced wound healing time of the individual can be related to the production of granulocytes which require glucose as their source of energy and as glucose as is not entering the cells energy is not being provided to the cells for the uptake of amino acids. Because of this proteins cannot be synthesized in the cells. All these factors lead to reduced wound healing in the tissues. In polyuria the urinary output of a person is increased in diabetes, in polydipsia the person gets thirsty again and again and lastly polyphagia increases the appetite of the person (Lawal 2008; Deshpande et al 2008). Diabetes mellitus is said to be working as a slow poison in the body and it can affect many processes in the body. It is noted that Diabetes Mellitus can further cause a huge damage to the different systems of the body. Neuropathy, nephropathy, retinopathy, cardiovascular stroke and peripheral vascular diseases are common diseases caused by the chronic processes of diabetes. In neuropathy the nerve cells of the body are damaged because of which the autonomic nervous system is affected usually. In retinopathy the macular retina of an individual is destroyed and this can lead to blindness. In nephropathy it can be seen that diabetes causes an alteration in the structure of the kidneys. And this may also lead to kidney failures in the long term if not treated properly. It is also seen that diabetes is related to the blood pressures as it is a major cause of hypertension nowadays. Because of hypertension the individuals also tend to develop ischemic heart diseases which further lead to hypoxia in the heart muscles and thus cardiac failure or cardiac stroke may occur. Peripheral Vascular Disease is another major disease caused by diabetes in the body. Diabetes can directly act on the blood vessels and narrow them. The most affected blood vessels by diabetes are the ones leading to the stomach, legs, arms and kidneys. After these vessels get narrowed it is necessary that the original form of the vessels is restored so that the blood supply is back to normal to these tissues. If this does not happen then amputation or removal of the tissue from the body is the only solution. Diabetes is a process which affects different processes being carried out in the body. As glucose is an important source of energy for almost all the cells in the body, diabetes may restrict this source of energy from being consumed and it would rather cause other diseases to develop in the body (Lawal 2008; Deshpande et al 2008). Huntington Disease Huntington disease is a hereditary disease in which progressive degeneration of the nervous tissue occurs. Huntington disease is caused by autosomal dominant mutation on Huntingtin gene. The autosomal dominant inheritance means that the affected person inherits one copy of gene with an increased number of trinucleotide from the affected parent. In autosomal dominant inheritance each offspring of the affected person has 50% risk of transmitting the mutant allele. When both the parents have one mutant allele then their offspring has 75% risk of transmitting the disease. Persons with both the genes affected are very infrequent. The huntingtin gene(HTT) is a gene which codes for Huntingtin protein. A portion of this gene is repeated known as trinucleotide repeat. The length of the trinucleotide repeat varies in individuals and generation. If the length of the trinucleotide repeat exceeds the threshold a new form of protein will be formed called mutant Huntingtin protein(mHtt). The normal huntingtin gene(HTT) holds a series of three DNA bases, which are cytosine, adenine and guanine(CAG). The CAG sequence of bases is repeated several times forming trinucleotide repeat(………CAGCAGCAG……..). This sequence of DNA bases codes for amino acid glutamine, so the repeated trinucleotide (CAG) produce polyglutamine tract also known as polyQ tract and the portion of the gene where the repeatition of the nucleotide occur is called as polyQ region. In normal gene the polyQ region contain less than 36 repeated trinucleotide whose outcome is the production of protein Huntingtin. Conversely gene containing 36 or more than 36 trinucleotide in the polyQ region results in the formation of altered form of Huntingtin protein, the mutant protein. This mutant Huntingtin protein functions abnormally and is lethal to different tissues especially brain tissue or nervous tissue. The damage to brain tissue in Huntington disease causes motor abnormalities, cognitive disturbances and psychiatric disturbances (Ross 2004; Robbins et al 2005). The signs and symptoms typically begin after the age of 35years and before 50 years. Death occurs usually 15 to 20 years after the onset of signs and symptoms. The most common motor abnormality is chorea which is the characteristic symptom of Huntington disease. Chorea are jerky, abnormal, random and uncontrollable movements and chorea is also known as choreoathetosis. Voluntary and involuntary mmovements are disturbed in Huntington disease. Disturbed voluntary movements in Huntington disease are abnormal eye movements, uncoordinated and slow fine movements and gait disturbances. Cognitive disturbances also accompany motor disturbances in Huntington disease. Cognitive abnormalities involve difficulty in planning, abstract thinking, rule acquisition. Memory deficit also appear and the deficit may be short term memory deficit or long term memory deficit. Dementia can also occur in worst conditions. Psychiatric disorders are also the symptoms of Huntington disease. Psychiatric disturbances are depression, anxiety, irritability, apathy or lack of initiative, aggressiveness, delusion and compulsion. When the mutant gene is expressed outside the brain it affects the peripheral tissue and the abnormalities caused are cardiac failure, muscle atrophy, impaired glucose tolerance, testicular atrophy, osteoporosis and weight loss (Robbins et al 2005; Langman & Sadler 2006). Down Syndrome Down syndrome is not a disease but is rather a syndrome. Down syndrome is a condition which is caused by the abnormality in chromosomes. The chromosome affected in Down syndrome is chromosome 21. Normal individuals have normal count of chromosome and in human normal count is 46 chromosomes. In 95% of Down syndrome affected people there is a presence of an extra chromosome 21(trisomy 21) and due to this extra chromosome their chromosomal count is 47. Meiotic nondisjunction of chromosome 21 occurs in the ovum during maternal age which causes trisomy 21. Recent studies have revealed that in 95% of trisomy cases, the origin of the extra chromosome is maternal. In 4% to 5% of the Down syndrome affected people do not have extra copy of chromosome but they contain extra chromosomal material. The extra chromosomal material comes from the Robertsonian translocation of chromosome 21 to another acrocentric chromosome like chromosome 14 or chromosome 22. About 1% of the people having Down syndrome are mosaic, which means that they have mixture of cells with chromosome 46 and chromosome 47. The mosaism is an outcome of the mitotic nondisjunction of chromosome 21 in early embryogenic period (Langman & Sadler 2006). The clinical features of Down syndrome are flat facial profile, oblique palpebral fissure and Epicanthic folds are also reported in Down syndrome. Down syndrome causes mental retardation and about 80 % of the affected people have IQ less than 50. Around 40% of the patients have congenital heart diseases. The most common defects are endocardial cushion defects which include atrial septal defects, ostium primum defects, ventricular septal defects. Congential disturbances in oesophagus and small bowel are also seen in Down syndrome. Children with Down syndrome have increased risk of acute leukemia. Acute lymphoblastic leukemias and acute myeloid leukemia occur in Down syndrome. Patients aging above 40 having trisomy 21 develop Alzheimer disease which is a degenerative brain disorder. Down syndrome affects immunity in such a way that the patients are susceptible to serious infections (Robbins et al 2005; Langman & Sadler 2006). Bibliography Deshpande, A. D., Harris-Hayes, M., & Schootman, M. (2008). Diabetes Special Issue - Epidemiology of Diabetes and Diabetes-Related Complications. Physical Therapy.88 (11), 1254. Kumar, V., Abbas, A. K., Fausto, N., Robbins, S. L., & Cotran, R. S. (2005). Robbins and Cotran pathologic basis of disease. Philadelphia: Elsevier Saunders. Top of FormLawal, M. (2008). Management of diabetes mellitus in clinical practice. British Journal of Nursing : BJN. 17 (17), 1106.Top of FormTop of Form Ross, C. A. (January 01, 2004). Huntingtons Disease - New Paths to Pathogenesis. Cell, 118, 1, 4. Bottom of Form Top of Form Sadler, T. W., & Langman, J. (2006). Langmans medical embryology. Philadelphia: Lippincott Williams & Wilkins. Bottom of Form Read More