What Students Need to Know about Chromosomal Abnormalities

Chromosomes are stickshaped structures in the middle of each cell in the body. Each cell has 46 chromosomes grouped in 23 pairs. When a chromosome is abnormal, it can cause health problems in the body. Abnormal chromosomes most often happen as a result of an error during cell division. Chromosome abnormalities often happen due to one or more of these: Errors during dividing of sex cells (meiosis) Errors during dividing of other cells (mitosis) Exposure to substances that cause birth defects (teratogens) There are several different genetic syndromes caused by missing or extra chromosomes, including: Trisomy 21 or Down syndrome Turner syndrome Trisomy 18 Trisomy 13 In addition, there are many microdeletion and microduplication syndromes caused by small chromosomal changes, the most wellknown of which is 22 q11. 2 deletion syndrome. Chromosome abnormalities, depending on their size or location, can cause a variety of birth defects and dysmorphic facial features an