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Klinefelter syndrome is the most common sex chromosome aneuploidy in humans. It represents the most frequent cause of hypogonadism and infertility in men. Most cases are caused by nondisjunction errors in paternal meiosis I. [2] About eighty percent of individuals with this syndrome have one extra X chromosome resulting in the karyotype XXY ...
The syndrome is defined by the presence of at least one extra X chromosome in addition to a Y chromosome, yielding a total of 47 or more chromosomes rather than the usual 46. Klinefelter syndrome occurs randomly. The extra X chromosome comes from the father and mother nearly equally.
49,XXXXY syndrome is an extremely rare aneuploidic sex chromosomal abnormality. It occurs in approximately 1 out of 85,000 to 100,000 males. [1] [2] [3] This syndrome is the result of maternal non-disjunction during both meiosis I and II. [4] It was first diagnosed in 1960 and was coined Fraccaro syndrome after the researcher. [2]
XYY syndrome, also known as Jacobs syndrome, is an aneuploid genetic condition in which a male has an extra Y chromosome. [1] There are usually few symptoms. [2] These may include being taller than average and an increased risk of learning disabilities. [1] [2] The person is generally otherwise normal, including typical rates of fertility. [1]
Chromosome 21 from Human Genome Program Normal human Karyotype. Down syndrome is a chromosomal abnormality characterized by the presence of an extra copy of genetic material on chromosome 21, either in whole (trisomy 21) or part (such as due to translocations). The effects of the extra copy varies greatly from individual to individual ...
Sex chromosome aneuploidies are caused by nondisjunction, a process through which gametes (eggs or sperm) with too many or too few chromosomes are produced. In nondisjunction, homologous chromosomes or sister chromatids fail to separate properly when producing gametes. [10] XXXYY syndrome, by its nature, requires multiple steps of nondisjunction.
Full trisomy 13 is caused by nondisjunction of chromosomes during meiosis; the mosaic form is caused by nondisjunction during mitosis. Like all nondisjunction conditions (such as Down syndrome and Edwards syndrome), the risk of this syndrome in the offspring increases with maternal age at pregnancy, with about 31 years being the average. [2]
XX male syndrome, also known as de la Chapelle syndrome, is a rare intersex condition in which an individual with a 46,XX karyotype develops a male phenotype. [2] Synonyms for XX male syndrome include 46,XX testicular difference of sex development (or 46,XX DSD) [3] [4] [5] [6]