Turner Syndrome
Females with this syndrome have normal intelligence, are usually short, and will not go through puberty without hormone therapy. Because their ovaries fail to develop normally, almost all females with Turner syndrome are infertile. Karyotype for individuals with Turner syndrome is generally 45, XO. Occurance is 1:2500 females.
Klinefelter Syndrome
Occurance is ~1.2 in 1000 males. In Most Klinefelter Syndrome patients the karyotype is a 47, XXY, but in ~ 20% is 48, XXXY. Males with Klinefelter syndrome have low to average intelligence. Most appear normal at birth, but may develop breast tissue and female sexual characteristics. There may be an increased risk of psychotic disorders and adaptabiltiy disorders.
Down Syndrome
This condition is best known as Down syndrome but the name "Trisomy 21" is the most technically correct term. Incidence is between ~1:800 births and 1:1250 births. Many infants with this condition have poor muscle tone, a round flat face, protuding tongue,upward slanting eyes, small ears (perhaps without earlobes), flat nasal bridge, and stubby fingers. The degree of mental retardation varies greatly. For some it is minimal; for others it is substantial. Many also have a congenital heart defect. In 95% of cases, the karyotype is 47, XY,+21 or 47, XX,+21. The remaining 5% are translocaitons, mosaicisms, or partial trisomies. The risk of having a baby with Trisomy 21 depends on the age of the mother when the baby is born. The older the mother, the higher the risk.
Edward Syndrome
Sometimes called "Edwards's syndrome" but the name "Trisomy 18" is preferred. Incidence is ~1:8,000 births. Many infants with this condition have unusually shaped ears, protruding eyes, rocker bottom feet, and die very young (most before 1 year old). If the individual does survive there will be severe mental retardation. In 80% of cases, the karyotype is 47, XY,+18 or 47, XX,+18; 10% are mosaic, and the remaining 10% involve translocations or double aneuploidies like 48, XXY,+18.
Patau Syndrome
This is sometimes referred to as "Patau syndrome" but the name "Tisomy 13" is preferred. Incidence is estimated to be between 1:2,000 to 1:14,000 births. Most infants with this condition have cleft lip and/or cleft palate, extremely small eyes, extra digits, and die very young (most before 1 year old). Heart conditions and defects are common. Those that survive have severe mental retardation and no sense of smell due to missing olfactory bulbs. In 80% of cases, the karotype is 47, XY,+13 or 47, XX,+13. The remaining 20% are either mosaic or trisomy due to a translocation.
Jacobs Syndrome
Occurance is approximately 1 in 800 to 1 in 1000 male births. It is believed that individuals with this karyotype tend to have more volitile/criminalistic behavior, though most appear normal. The karyotype involves having an extra Y chromosome (47, XYY). There is a normal life expectancy.
Trisomy X
Incidence is 1:1250 female births. Individuals with this karyotype are prone to fertility problems. Studies also have suggested the possibility of increased risk for skizophrenia.
Cri-du-chat
Occurence is ~1:216000 births. There is an improperly developed larynx which causes a cat-like cry and a high arched palate. Individuals with this abnormality generally have a normal life expectancy, but will be retarded with IQ's less than 20. Some never learn to talk with this genetic disorder and have congenital heart disease.
Tay Sachs
Infants born with this disorder generally do not live beyond age 4. There is a mutation causing a deficiency of an enzyme called hexosaminidase A or Hex A. This allows a build up of fatty substances in the brain. Eventually, the child becomes blind, deaf, can no longer swollow, and becomes paralyzed.
Hemophilia
The word hemophilia derived from two Greek words: haima, meaning blood, and philia, meaning affection. The blood of a person with hemophilia does not clot normally. He does not bleed more profusely or more quickly than other people; however, he bleeds for a longer time. External wounds are usually not serious. Far more important is internal bleeding (hemorrhaging). These hemorrhages are in joints, especially knees, ankles and elbows; and into tissues and muscles. When bleeding occurs in a vital organ, especially the brain, a hemophiliac's life is in danger. Incidence is 1:10,000 for hemophilia A and 1:50,000 for hemophilia B.