A Change Of A Chromosome Number

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A change in a chromosome number is known as Aneuploidy. Aneuploidy is a genetic condition where an organism acquires fewer or more chromosomes than the normal diploid number. A monosomic organism has one less than the diploid number of chromosomes meaning the human zygote will have 45 chromosomes. A trisomic organism has one more than the diploid number of number of chromosomes i.e. the organism will now have 47 set of chromosome meaning there are three homologous copies of one chromosome. It can develop in many ways. For example, during mitosis a centromere can be deleted as a result a chromosome can be lost. Aneuploidy usually alters the phenotype drastically because it alters chromosome number but not the DNA sequence. Between 75 and…show more content…
Gene alterations on an organism have profound effects on both cellular and physiological levels. Aneuploidy can be present in two ways if its present in only certain cells its known as somatic aneuploidy but its its found in all of the cells then its called constitutional aneuploidy. The effects of constitutional aneuploidy can be lethal. In humans, a condition known as down syndrome is caused is due to third copy of chromosome 21 and a third copy in any autosome will always result in childhood problems. (Hassold TJ, 1984). They can survive but will have significant health problems and will be mentally affected. Also, the absence of any autosomal chromosomes can lead to embryonic death.

One of the basic consequences of aneuploidy is the genomic instability. Genomic instability refers to the change initiated during the life cycle of a cell. Genetic instability is hallmark of aneuploidy that leads to wide range of changes in the genome of the organisms. These changes can cause serious effects to the organism these include the chromosome alterations, chromosomal mutations. The Structural rearrangements of chromosomes are thought to develop from the repair of double-strand DNA breaks (DSB) by non- homologous end joining (NHEJ) pathway and its variant, alternative NHEJ (also known as backup NHEJ) (Quinlan and Hall, 2012).
During a cell division, it is believed that genomic instability is minimized by four major mechanisms, which include chromosome segregation in
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