This is a research paper regarding down syndrome and genetic components involved in the disease.
- Introduction
The human body usually consists of cells, and each cell has a nucleus (Margulies, 2007). Inside the nucleus there are genes that determine the character traits inherited from parents. These genes are grouped in structures referred to as Chromosomes. In normal conditions, the nucleus carries 23 pairs of chromosomes. Down syndrome is a condition that occurs when the nucleus an extra chromosome 21, either fully or partially. The extra chromosome adds genetic materials that interfere with body development, leading to characteristics common in Down syndrome. One of the physical symptoms of a Down syndrome is that it causes small stature, low muscle tone, slanting eyes and deep crease on the palm (Margulies, 2007). However, people with Down syndrome differ in terms of character traits, and some people may not even exhibit these characteristics.
Down syndrome is the most prevalent condition caused by genetic issues. In America for instance, one in six hundred babies develops Down syndrome at birth. Currently, there are approximately 400,000 people with Down syndrome in USA (Morawiec et al, 2014). This condition was discovered in 1959 when Jerome Lejuene, a French scientist carried out a study and realized that people with 47 chromosomes in their cells instead of 46 have common characteristics that are now attributed to the Down syndrome.
2. Detailed Descriptions
- Heredity
The Down syndrome can be hereditary. For example, a translocation Down syndrome is caused when an unaffected parent passes a balanced translocation of chromosomes to his or her offspring. A balanced translocation occurs when genetic materials in the parent are rearranged between chromosome 21 and an extra chromosome. A balanced translocation does not result in any loss or gain of genetic material in the parent, but the translocation becomes unbalanced as it is inherited by the offspring (Margulies, 2007). As the baby inherits unbalanced translocation, he or she may gain an extra genetic material from chromosome 21, leading to the Down syndrome. Errors may also occur during meiosis, leading to trisomy Down syndrome. In this case, one pair of the chromosomes does not divide during meiosis, causing one cell to have more chromosomes than the other. This is called non-disjunction. During reproduction, the abnormal egg may merge with a normal sperm or vice versa, leading to three extra 21st chromosomes which cause the trisomy Down syndrome/
- Molecular genetics
DNA structure and replication is one of the common causes of Down syndrome. Down syndrome may result from occasional errors caused by molecular abnormalities during DNA replication. DNA is a small molecule which carries instructions that make up living organisms. The DNA has a three dimensional structure, and one of its functions is replication (Morawiec et al, 2014). During replication, all genes of the original cell are copied to the new cell during cell division. Replication is very accurate because DNA is a very stable molecule. However, mistakes may occur occasionally and result in errors. A good example is the Down syndrome which occurs due to an error in cell division. When the DNA copies its genes during replication, it may make an occasional error by copying three chromosomes instead of two in one of the two cells formed during cell division. This results in Down syndrome.
- Genetic Variation
The Down syndrome may also be caused by genetic variation. This concept implies that genes vary within populations or across different populations. Mutation is a major cause of genetic variation. It refers to permanent alteration of chemical genetic structure. Changes in genes may be passed on to new cells formed during cell division. Such genetic changes may occur due to errors of the DNA during replication, causing an extra chromosome within one of the cells (Margulies, 2007). This causes Down syndrome.
DNA repair is also related to the Down syndrome. DNA molecules can sometimes be damaged by environmental conditions or metabolism in the body of a human being. This damage on the DNA may limit the ability of the cell to perform its function of genetic transcription. If the normal DNA repair fails, the DNA damage may become irreparable. This causes cross-linkages or double strand breaks of the DNA. A cell with an irreparable DNA may enter the state of unregulated cell division among other abnormal states. Consequentially, unregulated cell division may result in the replication of an extra 21 chromosome on one of the cells. This additional 21 chromosome is of course responsible for the Down syndrome.
Population genetics refers to the study of genetic and allele distributions in a population. It includes the processes of mutation, natural selection, and genetic drift. When populations interact, they exchange alleles and genes, which is common in evolution concepts (Halliburton, 2004). Natural selection occurs when a species is able to reproduce and survive within a population. On the other hand, genetic drift occurs when there is a random sample of the parent’s alleles in the offspring. These concepts apply in the Down syndrome because they both explain the exchange of alleles and genetics across populations or within members of the same species in a population (Halliburton, 2004). When such genes are exchanged, an extra chromosome 21 may be copied, causing the Down syndrome. Reproductive isolation in population genetics may occur when two chromosomes from the male and female species fail to pair up during meiosis. This may cause an extra chromosome 21 that causes Down syndrome.
Lastly, multifactorial traits also relate to the Down syndrome. During multifactorial inheritance, many factors contribute to the birth defects of a child. Genetic and environmental factors cause such multifactorial traits as genes from both parents interact. Even if some people inherit the same genes from their parents, environmental factors may influence their character traits, causing multifactorial disorder (Morawiez et al, 2014). When genetic and environmental factors affect the cell division, an additional 21 chromosome may occur, leading to the Down syndrome.
- Bioethical issues related to genetic analyses and manipulation
Down syndrome may be occasioned by genetic analysis and manipulation during genetic engineering. Ethical concerns have been raised concerning the artificial mechanisms of manipulating genetic make ups in animals and human beings in order to achieve certain character traits (Karnein, 2012). In some cases, such manipulations may lead to conditions that cause the Down syndrome. Bioethical issues concerning genetic manipulations should therefore be addressed in a balanced manner.
Those who support genetic manipulation through genetic engineering technologies argue that it merges desired capabilities (Karnein, 2012). However, communities and governmental bodies have cited laboratory risks as a key disadvantage of the practice (Karnein, 2012). Genetic analysis may lead to decisions by individuals to alter their reproductive behavior. Biotechnology has resulted in isolation of DNA sequence in one specifies and attaching it to a different species. This may result in errors in cell division, causing Down syndrome. Furthermore, cell fusion may be carried out by merging two cells from different people or animals so that the hybrid cell is able to continue functioning and reproducing. This fusion may also lead to abnormalities that add an extra 21 chromosome to one cell, causing the Down syndrome.
Opponents of the genetic engineering argue that the practice is not ethical because it alters the natural forms of life (Karnein, 2012). Religiously, people content that it is against the wishes of God. Those who oppose from a non-religious perspective argue that it is not ethical because it results in alterations that make human beings or animals to experience conditions that are not determined by nature (Karnein, 2012).
References List
Halliburton, R. (2004). Introduction to Population Genetics. Upper Saddle River, NJ: Prentice Hall
Karnein, A.J. (2012). A theory of unborn life: From abortion to genetic manipulation. Oxford: Oxford University Press.
Margulies, P. (2007). Down syndrome. New York: Rosen Pub. Group.
Morawiec, Z., Janik, K., Kowalski, M., Stetkiewicz, T., Szaflik, J., Morawiec-Bajda, A., Sobczuk, A. and Blasiak, J. (2014). DNA damage and repair in children with Down’s syndrome. Mutation Research, 637(2), 118-123.
