18 are the most common. In rare cases, a fetus with Trisomy 13 can survive, giving rise to Patau syndrome. Autosomal trisomy can be associated with birth defects, intellectual disability and shortened life expectancy. Trisomy of sex chromosomes can also occur and include: XXX (Triple X syndrome) XXY (Klinefelter syndrome) XYY (Jacobs syndrome) Compared to trisomy of the autosomal chromosomes, trisomy of the sex chromosomes normally has less severe consequences. Individuals may show few or no symptoms and have a normal life expectancy. See also Chromosome abnormalities Aneuploidy Karyotype Sexual reproduction Monosomy References External links Cytogenetics Chromosomal abnormalities