Also Beta cells have many organelles and there is mitochondria present, which in a prokaryotic cell there are fewer organelles and there aren’t any mitochondria present. A normal gamete either a sperm or egg contains one copy of each chromosome. However, this procedure is not flawless and chromosome abnormalities may occur when chromosomes fail to segregate properly. While the fetus with Down Syndrome is developing, its body cells do not reproduce as … Introduction Down syndrome is the most common genetic disordered that causes developmental delay. Essay traffic rules my father essay grade 1: reflective summary on prescribing practice learning nursing essay. The characteristics of Down syndrome are linked to genes present in the additional copy of chromosome 21. Old cells die and need to be replaced. Mendel's law of segregation states that when a person produces gametes, the copies of the gene separate and each gamete obtains one copy only. Those with trisomy 21, exhibit a flat face with small broad nose and their ears are irregularly shaped. Down syndrome is a genetic disorder that occurs as a result of an additional chromosome. Then late in the prophase, One of the nondisjunction is trisomy 21 or also known as Down’s syndrome. As frustrating, life altering, and challenging as the diagnosis of February 4, 2015 Chromosome segregation is the coordinated movement of chromosomes to the opposite poles of cell during cellular reproduction or mitosis of during production of sex cells or meiosis. Human and animal studies are also playing a critical role in understanding the functions of the identified genes. In conclusion, Down syndrome is a genetic disorder caused by an additional twenty first chromosome. People with this type of chromosomal arrangement are phenotypically normal. Down syndrome, the most common genetic birth defect associated with mental retardation, occurs equally across all races and levels of society. Nondisjunction during meiosis 1 and during meiosis two both leads to generation of gametes that are disomic, implying that there is an additional chromosome, or nullisomic, implying that a chromosome is lost. Maternal age is a risk factor for conceiving a child affected with Down Syndrome. Chromosomes in cells are made up of proteins and genetic information in form of DNA. Numerical abnormalities usually emerge as a result of failure of the chromosomes to properly segregate, a phenomenon referred to as disjunction. Mosaic Down Syndrome occurs when some body cells are normal and other cells possess trisomy 21, an arrangement known as mosaic. Instead of chromosome 21 separating and moving to opposite regions of the cell during meiosis, they fail to detach resulting to disjunction which makes the reproductive cell to have abnormal number of chromosomes. As they get older, people with Down syndrome are more likely to suffer from mental health issues, like depression. The exchange of genes amid chromosomes, usually referred to as crossing over, normally occurs during meiosis, when the total chromosome number is halved. There are other distinguishable appearance for those who have trisomy 21 but these are the most, A Comparison Of Their Eyes Were Watching God And Of Mice And Men, Environmental Impacts: The Impact Of Genetically Modified Foods, Literary Analysis: The Neckless By Mme Loisel, Human Psychology In The Cask Of Amontillado. service and earn bonuses
The person has a single copy of the material on short arm of chromosome 21, but it does not have an apparent effect. At the point of chiasmata, there is a chance in which the chromosomes undergo crossing over where an exchange of genes between the two homologous chromosomes takes place. Some of the features include flattened nose and face, small mouth and occasionally long tongue, small ears, short neck and slanting eyes having small skin folds. The person possesses two copies of everything on chromosome number 14, and two copies of all material on long arm of chromosome 21( Costa, & Patterson, 2005 ). Down syndrome, also known as Trisomy 21, is a genetic disorder that results from an individual having an extra copy of chromosome 21. Chromosomes are inherited as a cluster implying that at the time of cell division, they function as a unit other than independently.
A risk of 1 per cent also exists for parents who have conceived a child having Down syndrome. Many individuals with Down syndrome have identifiable physical symptoms, though these symptoms depend on the severity. © 2006-2020 EssaysProfessors.com. This may take place as a result of a nondisjunction occurrence during early stages of cell division resulting to a portion of the cells with trisomy21. Down syndrome may also be caused by a chromosome translocation, which is a chromosome anomaly caused by rearrangement of portions between non-homologous chromosomes deviation in the composition of genes within a chromosome takes place when a chromosome breaks, and the broken parts connect with partner chromosome if the breakage has occurred in similar locations (Hattori, 2000). Nondisjunction during first division of meiosis emerges from the failure of the homologous chromosomes to separate out to opposite poles of cell.
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In order to proceed into meiosis, the cell must replicate its DNA and prepare for cell division during interphase. 5371 words (21 pages) Essay. In Translocation Down Syndrome, the additional material in chromosome 21 occurs as result of Robertsonian translocation which usually entails exchange of genetic material between nonhomologous chromosomes. No matter how you voted, everyone’s a winner on Election Day. These Page proteins cause the typical features of Down Syndrome. In Down syndrome, an individual inherits two chromosomes 21 from one parent instead of one, and one chromosome 21 from the other parent, leading to three copies of chromosome 21 instead of two copies. This affirms that the older the mother, the higher rate of exposure. Conclusion Of Down Syndrome; Conclusion Of Down Syndrome. An estimation of about 95 per cent of children and adults affected by this disorder has the whole chromosome 21. with EssaysProfessors, Tell your friends about our Binary fission is a quick and simple process involving replication, elongation, separation, and daughter cells. The inheritance of the three chromosomes 21 causes Down Syndrome, and that is why it is also known as trisomy 21.
Adults with Down Syndrome are now living longer – the average life expectancy is now between 50 and 60 years old with some people even reaching their 70s. Therefore, normal sperm and egg cells have only 23 chromosomes instead of 46 chromosomes as somatic cells (Mays, 2006). John Langdon Down described the condition hence named after him. It may also occur when an embryo with Down syndrome experiences nondisjunction and some of cells within the embryo regress back to normal chromosomal arrangement. When cells with nondisjunction error unite with a typical cell, the fertilized egg ends up having uneven number of chromosomes.
The Mendel's, the law of independent assortment and the law of segregation form the foundation of genetics. Down Syndrome Essays (Examples) Filter results by: Number of pages 1-5 pages 6-10 pages 11-15 pages 16-20 pages 21-25 pages 26-30 pages 31-40 pages 41-50 pages 51+ pages Segregation occurs as a result of separate carriage of genes on the chromosomes, which are not blended or altered through forming pairs (Pierce, 2005).
The person also has 47 chromosomes in the cells instead of the normal 46 which leads to physical and mental retardation with abnormal physical characteristics such as large tongue, flat face and slanting eyes.
However, they believe that the additional genes interrupt the relations between the actual genes of the chromosome 21 and other genes. Once the preparations are done, the cell enters prophase I where DNA supercoils to condense into chromosomes, and the chromosomes pairs up with its homologous chromosome. This leads to one of the newly formed cells possessing 24 chromosomes and the other possessing 22 chromosomes, an error called nondisjunction (Antonarakis, 2004).
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