In particular, risk of aneuploidy is increased by tobacco smoking, and occupational exposure to benzene, insecticides, and perfluorinated compounds. Increased aneuploidy is often associated with increased DNA damage in spermatozoa. Structural abnormalities
When the chromosomes structure is altered, this can take several forms:
Deletions: A portion of the chromosome is missing or has been deleted. Known disorders in humans include Wolf–Hirschhorn syndrome, which is caused by partial deletion of the short arm of chromosome 4; and Jacobsen syndrome, also called the terminal 11q deletion disorder. Duplications: A portion of the chromosome has been duplicated, resulting in extra genetic material. Known human disorders include Charcot–Marie–Tooth disease type 1A, which may be caused by duplication of the gene encoding peripheral myelin protein 22 (PMP22) on chromosome 17. Inversions: A portion of the chromosome has broken off, turned upside down, and reattached, therefore the genetic material is inverted. Insertions: A portion of one chromosome has been deleted from its normal place and inserted into another chromosome. Translocations: A portion of one chromosome has been transferred to another chromosome. There are two main types of translocations:
Reciprocal translocation: Segments from two different chromosomes have been exchanged. Robertsonian translocation: An entire chromosome has attached to another at the centromere - in humans, these only occur with chromosomes 13, 14, 15, 21, and 22. Rings: A portion of a chromosome has broken off and formed a circle or ring. This can happen with or without the loss of genetic material.
A chromosomal abnormality, chromosomal anomaly, chromosomal aberration, chromosomal mutation, or chromosomal disorder, is a missing, extra, or irregular portion of chromosomal DNA. These can occur in the form of numerical abnormalities, where there is an atypical number of chromosomes, or as structural abnormalities, where one or more individual chromosomes are altered. Chromosome mutation was formerly used in a strict sense to mean a change in a chromosomal segment, involving more than one gene. Chromosome anomalies usually occur when there is an error in cell division following meiosis or mitosis. Chromosome abnormalities may be detected or confirmed by comparing an individuals karyotype, or full set of chromosomes, to a typical karyotype for the species via genetic testing. Numerical abnormality
An abnormal number of chromosomes is called aneuploidy, and occurs when an individual is either missing a chromosome from a pair (resulting in monosomy) or has more than two chromosomes of a pair (trisomy, tetrasomy, etc.). Aneuploidy can be full, involving a whole chromosome missing or added, or partial, where only part of a chromosome is missing or added. Aneuploidy can occur with sex chromosomes or autosomes.An example of trisomy in humans is Down syndrome, which is a developmental disorder caused by an extra copy of chromosome 21; the disorder is therefore also called trisomy 21.An example of monosomy in humans is Turner syndrome, where the individual is born with only one sex chromosome, an X. Sperm aneuploidy
Exposure of males to certain lifestyle, environmental and/or occupational hazards may increase the risk of aneuploid spermatozoa.