What does it mean to have an extra chromosome?

Someone who has an extra chromosome has 47 total chromosomes instead of the typical 46 or 23 from each parent. This results in a condition known as trisomy . Trisomy is associated with mental retardation and often death, depending on which chromosome has malfunctioned.

Trisomy occurring on chromosomes 13 or 18 results in severe mental retardation. Babies born with this condition usually die of medical complications within days, and sometimes sooner. The vast majority of chromosomal disorders occur early in pregnancy and cause the fetus to abort itself, resulting in miscarriage. Therefore, most babies with an extra chromosome die.

However, in one condition, children can live and even have productive lives if given treatment and special education and care. Babies born with trisomy 21, or an extra chromosome 21, have a condition known as Down's Syndrome . Although children with Down syndrome suffer from some form of mental retardation, most of them are highly functioning.

Children with Down syndrome generally have a distinctive physical appearance, with smaller-than-normal heads and eyes that are rounded at the ends rather than pointed. They may also have poor muscle tone, small ears and mouths, and broad hands with short fingers. The mental abilities of these children vary widely, but most can live productive lives if the right interventions are taken early.

A mother is more likely to have a child with an extra chromosome as she ages. This could be because her eggs are aging and more likely to have chromosomal defects than those of a younger woman. There is no known prevention for Down syndrome, although diagnostic tests can be done during pregnancy to determine if a fetus has the condition. These are not always accurate, as most babies with abnormal tests do not have Down syndrome.

In addition to physical characteristics and mental differences in children born with an extra chromosome, serious health conditions can often occur. These can include vision problems, intestinal blockages, heart problems including an enlarged heart, constipation, sleep apnea, and hypothyroidism. Many of these things can be successfully treated, although serious heart conditions may require surgery to correct.

The diagnosis of Down syndrome can usually be made based on the results of blood tests that look for an extra chromosome 21. Suspected Down syndrome will usually occur right at birth, though when the doctor notices the typical physical features common with trisomy 21. The baby will be examined. for additional health problems once a diagnosis has been made.

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