The process of pairing with its homologous chromosome in the chiasmata is called synapsis, which would result in the formation of a tetrad. As a result, the activity of some genes will be more than usual or below the usual. In trisomy 21 case, an extra chromosome is found on chromosome 21 and thus causing cells to have difficulty in regulating the amount and type of protein that was made. CONCLUSION. In conclusion, Down syndrome is a genetic disorder caused by an additional twenty first chromosome. This nondisjunction occurs in anaphase I where the homologous pairs did not separate properly, leading to having an extra chromosome in two gametes and missing a chromosome in the others. Translocation Down syndrome might be de novo, implying that they are not inherited but occurring at the period when an individual is being conceived. According to the National Down Syndrome Society, roughly 400,000 Americans have Down Syndrome … 1(877)733-3925. Chromosomes are inherited as a cluster implying that at the time of cell division, they function as a unit other than independently. Down syndrome is a genetic disorder that occurs as a result of an additional chromosome. 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. Down syndrome is a genetic disorder that occurs as a result of an additional chromosome. However, they believe that the additional genes interrupt the relations between the actual genes of the chromosome 21 and other genes. Chromosomes separate along a spindle fiber that joins at a site known as the kinetochore to chromosome centromere during the anaphase stage of mitosis. During mitosis, once cell divides into two cell having the same type and number of chromosomes as parent cell. While the fetus with Down Syndrome is developing, its body cells do not reproduce as … Cell Cycle and Mitosis 5371 words (21 pages) Essay. The symptoms of Down syndrome are linked to genes present in the additional copy of chromosome 21. The Mendel's law of independent assortment, also known as law of inheritance, states that all alleles of diverse genes sort out independently of each other during gamete formation. However during cell division, a chromosome fails to detach and stays connected with its pair chromosome. Trisomy 21 causes approximately 95 percent of Down syndrome, with 88 percent coming from meiotic nondisjunction in maternal gamete and 8 percent from nondisjunction in paternal gamete. The severity of the condition depends on the types and number of extra genes inherited by an individual. During meiosis, chromosomes are required to divide and go to diverse regions of the cell, a meiotic step known as disjunction. Segregation occurs as a result of separate carriage of genes on the chromosomes, which are not blended or altered through forming pairs (Pierce, 2005). Statistical studies about downs syndrome reveal that it affects 1 of 800 live births and this is the major causative factor for cognitive impairment. As frustrating, life altering, and challenging as the diagnosis of People with this type of chromosomal arrangement are phenotypically normal. Errors taking place during mitosis or meiosis can result to chromosomal aberrations where large portions of chromosomes or whole chromosomes are added or missing. The long arm of chromosome number 21 is connected to another chromosome, usually chromosome 14 or itself. An estimation of about 95 per cent of children and adults affected by this disorder has the whole chromosome 21. Mosaic Down Syndrome occurs when some body cells are normal and other cells possess trisomy 21, an arrangement known as mosaic. Korenberg (2004) argues that rearrangements of this form may be balanced, implying that there isn't a loss of genetic material, or unbalanced, implying that there is a loss or gain of a portion of the chromosome. Biology 001 Laboratory Section 5 They also display moderate to severe physical and mental retardation, and usually grow and develop more slowly than their peers. The presence of linkage groups attributes to the reason why some traits like Down syndrome do not abide by the Mendel's law of independent assortment of recombination of the genes and the traits that these genes control. OpenStax states that the process of new cells being made is called cell division (2013). Nondisjunction during first division of meiosis emerges from the failure of the homologous chromosomes to separate out to opposite poles of cell. They have short and broad hands with short fingers. Beta cells in the pancreatic tissue release insulin…, to make cells to survive. In order to proceed into meiosis, the cell must replicate its DNA and prepare for cell division during interphase. The effects of the disorder on physical and mental development are severe and are expressed throughout the life span. 767 Words 4 Pages. Josh Richardson © 2006-2020 Essay traffic rules my father essay grade 1: reflective summary on prescribing practice learning nursing essay. A normal gamete either a sperm or egg contains one copy of each chromosome. Down syndrome is caused by occurrence of an additional chromosome 21 which makes the person to have three copies of chromosome 21 instead of two. However, this procedure is not flawless and chromosome abnormalities may occur when chromosomes fail to segregate properly.

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