Down Syndrome
DOWN SYNDROME
Down Syndrome is a congenital disorder arising from a chromosome It comes from a defect involving chromosome 21. The condition leads to impairments in both cognitive ability and physical growth that range from mild to moderate developmental disabilities. Through a series of screenings and tests, Down syndrome can be detected before and after a baby is born.
The only factor known to affect the probability of having a baby with Down syndrome is maternal age. Less than one in 1,000 pregnancies for mothers less than 30 years of age results in a baby with Down syndrome. For mothers who are 44 years of age, about 1 in 35 pregnancies results in a baby with Down syndrome. Because younger women generally have more children, about 75 - 80% of children with Down syndrome are born to younger women.
Cause of Down Syndrome
Down syndrome occurs because of an abnormality characterised by an extra copy of genetic material on all or part of the 21st chromosome. There are normally 46 chromosomes in each cell, 23 inherited from your mother and 23 from your father. When some or all of a person 's cells have an extra full or partial copy of chromosome 21, the result is Down syndrome.
The most common form of Down syndrome is known as Trisomy 21, a condition where individuals have 47 chromosomes in each cell instead of 46. This is caused by an error in cell division called nondisjunction, which leaves a sperm or egg cell with an extra copy of chromosome 21 before or at conception. Trisomy 21 accounts for 95% of Down syndrome cases, with 88% originating from nondisjunction of the mother 's egg cell. (Robertsonian) Translocation Down syndrome occurs when part of chromosome 21 becomes attached (translocated) onto another chromosome (usually chromosome 14), before or at conception. Children with translocation Down syndrome have the usual two copies of chromosome 21, but they also have additional material from chromosome 21 attached to the translocated
Down Syndrome is a congenital disorder arising from a chromosome It comes from a defect involving chromosome 21. The condition leads to impairments in both cognitive ability and physical growth that range from mild to moderate developmental disabilities. Through a series of screenings and tests, Down syndrome can be detected before and after a baby is born.
The only factor known to affect the probability of having a baby with Down syndrome is maternal age. Less than one in 1,000 pregnancies for mothers less than 30 years of age results in a baby with Down syndrome. For mothers who are 44 years of age, about 1 in 35 pregnancies results in a baby with Down syndrome. Because younger women generally have more children, about 75 - 80% of children with Down syndrome are born to younger women.
Cause of Down Syndrome
Down syndrome occurs because of an abnormality characterised by an extra copy of genetic material on all or part of the 21st chromosome. There are normally 46 chromosomes in each cell, 23 inherited from your mother and 23 from your father. When some or all of a person 's cells have an extra full or partial copy of chromosome 21, the result is Down syndrome.
The most common form of Down syndrome is known as Trisomy 21, a condition where individuals have 47 chromosomes in each cell instead of 46. This is caused by an error in cell division called nondisjunction, which leaves a sperm or egg cell with an extra copy of chromosome 21 before or at conception. Trisomy 21 accounts for 95% of Down syndrome cases, with 88% originating from nondisjunction of the mother 's egg cell. (Robertsonian) Translocation Down syndrome occurs when part of chromosome 21 becomes attached (translocated) onto another chromosome (usually chromosome 14), before or at conception. Children with translocation Down syndrome have the usual two copies of chromosome 21, but they also have additional material from chromosome 21 attached to the translocated
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