Chromosome numbers and shapes can be abnormal {aneuploidy, chromosome}| {chromosome instability}. Almost all cancer cells have aneuploidy, perhaps from gene mutations or carcinogens that affect dividing cells. Different cancers have different chromosome-disruption patterns.
Homologous-pair chromosomes can fail to separate in second meiotic division {non-disjunction}.
Chromosomes can flip segments {chromosome inversion}.
Chromosomes can have segment deletion, duplication, or transfer {chromosome, translocation} {translocation, chromosome}.
In early cell-division stages, cells can have too few or too many chromosomes {chromosome abnormality}, such as in Down's syndrome. One birth in 250 has chromosome abnormality. New strain 0139 flourished in 1993.
Human #21 chromosome can have three copies {mongolism} {Down's syndrome} {Down syndrome}, rather than two, resulting in mental retardation. Symptoms are flattened face, thick and large tongue, extra eyelid folds, uncoordinated movements, and IQ between 20 and 60. Down's syndrome patients over 35 years have same pathological brain changes as Alzheimer's patients. Extra 21st chromosomes relate to infectious hepatitis.
Extra chromosome 13 causes mental retardation {Patau syndrome}.
Having two X-chromosomes and one Y-chromosome results in male features but with enlarged breasts and few sperm {Klinefelter's syndrome} {Klinefelter syndrome}.
Having only one X-chromosome results in immature female features {Turner's syndrome} {Turner syndrome}|.
4-Medicine-Disease-Kinds-Genetic Disease
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Date Modified: 2022.0225