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How Does Chromosome Fusions Increase The Number Of Chromosomes

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Chromosome “fusions” in Karyotype Evolution
Most of the genetic material in an organism is found in its chromosomes. The number of chromosomes in eukaryotic organisms can range from 1 to 600 for each haploid genome. Haploid genomes consist of genes that make up a set of chromosomes in a haploid cell, which contains of one set of chromosomes. Whereas in diploid cells, there are two sets of chromosomes. The characteristics of these chromosomes in a species is called a karyotype. The number of chromosomes in a species is usually unique to that species or population. However, it can increase or decrease by certain processes (Lysák, 1).
Chromosomes can increase in two ways, polyploidy and centric fusion. Polyploidy is the duplication of a chromosome set or sets, whereas in centric fusion, the centromere breaks and allows the original chromosome to split into two chromosomes. When the number of chromosomes decreases, it is called aneuploidy. This is caused when chromosomes or chromatids, one of the chromosome strands, separates incorrectly during cell division. The number of chromosomes can also be decreased as a result …show more content…

These chromosomes contain two centromeres, but they will only survive if one of the centromeres becomes inactive. If the two centromeres remain active and stay close together, they can turn into monocentric chromosomes. Although it has not been proved why the loss of centromeres occurs, it is believed to occur because of changes in gene expression. A possible reason that centromeres become inactive is because there is a loss of centromere-specific sequences. The changes in gene expressions happen with or after the removal of centromere-specific sequences. This is called centromere decay. However it undetermined how and when these centromeric sequences are removed (Lysák,

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