Chromosomal defects, also known as chromosomal disorders, are abnormalities that occur when there is an issue with a person’s chromosomes, the structures that hold our DNA. Each human cell normally contains 23 pairs of chromosomes, for a total of 46. However, if something goes wrong during cell division, a person may end up with too many or too few chromosomes, or with one or more chromosomes that are structurally altered.

Here are some examples of chromosomal defects:

  1. Down Syndrome (Trisomy 21): This is one of the most well-known chromosomal disorders and is caused by having an extra copy of chromosome 21. Down Syndrome is associated with physical growth delays, characteristic facial features, and mild to moderate intellectual disability.
  2. Turner Syndrome: This occurs when a female has only one fully functioning copy of the X chromosome, instead of two. Turner Syndrome can cause a variety of medical and developmental problems, including short height, failure of the ovaries to develop, and heart defects.
  3. Klinefelter Syndrome: This occurs in males when they have an extra X chromosome (XXY instead of XY). Symptoms can include small testes, low testosterone levels, infertility, and characteristics often associated with feminization, such as development of breast tissue and less body hair.
  4. Edwards Syndrome (Trisomy 18) and Patau Syndrome (Trisomy 13): These are caused by an extra copy of chromosomes 18 and 13, respectively. They both result in severe intellectual disability and physical abnormalities in many parts of the body. Most infants with these conditions do not live past the first year of life.
  5. Cri-du-chat Syndrome: This is caused by a deletion of the end of the short (p) arm of chromosome 5. It’s named after the characteristic cry of affected infants, which is similar to that of a meowing kitten, due to problems with the larynx and nervous system.
  6. Chromosome 22q11.2 deletion syndrome, also known as DiGeorge syndrome: This is caused by a missing piece (deletion) in chromosome 22. Symptoms can include heart defects, poor immune system function, a cleft palate, complications related to low levels of calcium in the blood, and behavioral disorders.

While some chromosomal conditions result from an inherited anomaly, most occur as random events during the formation of reproductive cells (eggs and sperm). Advanced maternal age increases the risk for certain chromosomal abnormalities, like Down Syndrome.

The symptoms, severity, and treatment options vary greatly depending on the specific chromosomal defect. Some are compatible with a normal lifespan and typical intelligence, while others cause severe disability and are life-threatening.

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