Polyploidy occurs when an extra copy of every chromosome is made, trisomy when only an extra copy of a single chromosome occurs. If an entire chromosome is absent, most frequently in Turner syndrome, the disorder is called a monosomy . Chromosome Mutations Structural rearrangements in chromosomes that can be detected microscopically by changes in the banding patterns produced by dye specific staining of chromosomes are said to be chromosomal mutations. Microduplications produce an extra exact copy of a specific region of a specific chromosome. Inversions re-order a segment of chromosome in backwards order.
Translocations occur when a piece of a chromosome attaches to another chromosome.
It is estimated that one in every 550 individuals on this earth may contain a balanced translocation. If three or more miscarriages occur in a family, unbalance should be suspected and the family's chromosomes investigated. Each parent contributes one of the vertical strands. Thousands of base pairs are needed for each gene. It is believed that the human genome has between 50,000 and 100,000 genes.