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Examples of aneuplody in humans Trisomy 21 Down’s Syndrome 47,XX,+21 47,XY,+21 1/660 to 1/800 live births 3% – 4% due to translocation 2% - 4% mosaic trisomy 21 (error in mitotic division) Down syndrome is a chromosomal condition that is associated with mental retardation, a characteristic facial appearance, and weak muscle tone (hypotonia) in infancy. People with Down syndrome are at an increased risk of heart defects, digestive problems such as gastroesophageal reflux, hearing loss, and other medical problems. Most cases of Down syndrome result from trisomy 21. A small percentage of cases occur when only some of the body's cells have an extra copy of the chromosome. These cases are called mosaic Down syndrome. Down syndrome can also occur when part of chromosome 21 becomes attached (translocated) to another chromosome before or at conception, although this is uncommon. Affected people have two copies of chromosome 21, plus extra material from chromosome 21 attached to another chromosome. These cases are called translocation Down syndrome. Trisomy 13 1/5000 to 1/10,000 live births • Trisomy 13 is associated with multiple abnormalities, including severe mental defects and defects of the brain that lead to seizures (hypsarrhythmia), apnea, deafness, and ocular (relating to the eye) abnormalities. • • • • • Patau Syndrome Bartholin-Patau syndrome Chromosomal imbalance syndrome, pair 13, trisomy chromosome 13 trisomy syndrome D1 Trisomy Trisomy 13 syndrome The eyes are small with defects in the iris (coloboma). Most infants have a cleft lip and cleft palate, and low-set ears. Congenital heart disease is present in approximately 80% of affected infants. Hernias and genital abnormalities are common. http://www.nlm.nih.gov/medlineplus/ency/article/001660.htm Most cases of Patau syndrome result from trisomy 13. A small percentage of cases occur when only some of the body's cells have an extra copy of chromosome 13, resulting in a mixed population of cells with a differing number of chromosomes. Such cases are sometimes called mosaic Patau syndrome. Patau syndrome can also occur when part of chromosome 13 becomes attached to another chromosome (translocated) before or at conception. http://ghr.nlm.nih.gov/condition=patausyndrome Trisomy 18 • • • • • • • • • Edward’s Syndrome Chromosomal imbalance syndrome, pair 18, trisomy Complete trisomy 18 syndrome E3 Trisomy Edward's Syndrome Trisomy 16-18 Trisomy E syndrome Trisomy 18 syndrome 1/3,000 to 1/6,000 live births Approximately 80 percent of cases occur in females. Infants born with Edwards syndrome have an extremely high mortality rate— only 5 to 10 percent of these infants survive the first year of life. Some characteristics of this condition are low birth weight; a small, abnormally shaped head; small jaw; small mouth; and clenched fists with overlapping fingers. Infants born with Edwards syndrome also have mental retardation, heart defects, and other organ malformations such that most systems of the body are affected. Most cases of Edwards syndrome result from trisomy 18. A small percentage of cases occur when only some of the body's cells have an extra copy of chromosome 18, resulting in a mixed population of cells with a differing number of chromosomes. Such cases are sometimes called mosaic Edwards syndrome. Very rarely, a piece of chromosome 18 becomes attached to another chromosome (translocated) before or after conception. http://ghr.nlm.nih.gov/condition=edwardssyndrome Triple X syndrome • • • • • • Trisomy X 47, XXX Triplo X syndrome Trisomy X 47,XXX XXX syndrome 1/1,000 to 1/1,500 live female births Triple X syndrome, also called trisomy X or 47,XXX, is characterized by the presence of one extra X chromosome in each of a female's cells. Most often, this chromosomal change causes no unusual physical features or medical problems. Females with triple X syndrome are sometimes taller than average and have an increased risk of learning disabilities and delayed speech and language skills. These characteristics vary widely among affected girls and women, however. Most females with triple X syndrome have normal sexual development and are able to conceive children. Triple X syndrome results from an extra copy of the X chromosome in each of a female's cells. Researchers are not yet certain why an extra copy of the X chromosome is associated with tall stature and learning problems in some girls and women. Some females with triple X syndrome have an extra X chromosome in only some of their cells. These cases are called 46,XX/47,XXX mosaics. http://ghr.nlm.nih.gov/condition=triplexsyndrome Klinefelter Syndrome • • • • Klinefelter's Syndrome 47,XXY XXY syndrome XXY trisomy 1/500 to 1/2,000 live male births Klinefelter syndrome is a chromosomal condition that affects male sexual development. Some males with the condition have low levels of the hormone testosterone beginning during puberty, which can lead to breast development (gynecomastia) and an increased risk of breast cancer, reduced facial and body hair, and an inability to father children (infertility). Boys with Klinefelter syndrome may also have difficulty with speech and language development. Klinefelter syndrome is caused by the presence of one or more extra copies of the X chromosome in a male's cells. Extra copies of genes on the X chromosome interfere with male sexual development, preventing the testicles from functioning normally and reducing the levels of testosterone. Most often, males with Klinefelter syndrome have two X chromosomes and one Y chromosome (XXY). Some males with Klinefelter syndrome have the extra X chromosome in only some of their cells; these cases are called mosaic XY/XXY. http://ghr.nlm.nih.gov/condition=klinefeltersyndrome 47, XYY syndrome • • • XYY Karyotype XYY syndrome YY syndrome 1/1,000 live male births Most often, this chromosomal change causes no unusual physical features or medical problems. Males with 47,XYY syndrome are sometimes taller than average and have an increased risk of learning disabilities and delayed speech and language skills. These characteristics vary widely among affected boys and men, however. Most males with 47,XYY syndrome have normal sexual development and are able to conceive children. 47,XYY syndrome is caused by the presence of a single extra copy of the Y chromosome in each of a male's cells. Researchers are not yet certain why an extra copy of the Y chromosome is associated with tall stature and learning problems in some boys and men. Some males with 47,XYY syndrome have an extra Y chromosome in only some of their cells. These cases are called 46,XY/47,XYY mosaics. http://ghr.nlm.nih.gov/condition=47xyysyndrome Turner syndrome • • • • • • Bonnevie-Ullrich Syndrome monosomy X TS Turner's Syndrome Ullrich-Turner syndrome 45,X 1/2,500 live female births Women with this condition tend to be shorter than average and are usually infertile, or unable to conceive a child, because of a loss of ovarian function. Other features of Turner syndrome vary among affected females and can include webbing of the neck, puffiness or swelling (lymphedema) of the hands and feet, skeletal abnormalities, heart defects, and kidney problems. Turner syndrome results when a female's cells have one normal X chromosome and the other sex chromosome is missing or altered. The missing genetic material affects development and causes the characteristic features of the condition. About half of individuals with Turner syndrome have monosomy X, which means each cell in a woman's body has only one copy of the X chromosome instead of the usual two copies. Turner syndrome can also occur if one of the sex chromosomes is partially missing or rearranged rather than completely missing. Some women with Turner syndrome have a chromosomal change in only some of their cells, which is known as X-chromosome mosaicism. Researchers have not yet determined which genes on the X chromosome are responsible for most signs and symptoms of Turner syndrome. They have, however, identified one gene called SHOX that is important for bone development and growth. Missing one copy of this gene likely causes short stature and skeletal abnormalities in women with Turner syndrome. http://ghr.nlm.nih.gov/condition=turnersyndrome