What causes chromosomal mutations/abnormalities?It is caused by nondisjunction.
Nondisjunction happens when there is a failure of either of two homologous chromosomes to pass to separate cells during the first meiotic division, or of the two chromatids of a chromosome to pass to separate cells during mitosis or second meiotic division. As a result, one daughter cell has two chromosomes or two chromatids, and the other has none. |
Aneuploidy is the presence of an abnormal number of chromosomes in a cell, for example a human cell having 45 or 47 chromosomes instead of the usual 46. It does not include a difference of one or more complete sets of chromosomes, which is called euploidy. |
Deletion involves the loss of a piece of chromosome. If a chromosome breaks and the parts do not reattach, the pieces may be lost. This is the most serious kind of chromosome mutation. Here, bits of genetic information are not available to the offspring.
Duplication occurs when one extra, but identical piece of chromosome is added to the normal chromosome. Inversion occurs when the pieces of chromosome break apart and pieces rejoin the same chromosome in a different order. Usually inversions have no harmful effects on the offspring. Translocation occurs when pieces of chromosome break apart and the pieces join a different chromosome. |