Anonymous
Anonymous asked in HealthDiseases & ConditionsOther - Diseases · 1 decade ago

Down Syndrome?

How does someone have Down Syndrome? (How is this disease transmitted) even though there is no specific cause?

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  • 1 decade ago
    Best Answer

    Down Syndrome which is also medically called trisomy 21 is not a disease it is a genetic defect. It is called trisomy 21 because of the gene location in the DNA that is affected.

    "Down syndrome occurs with equal frequency in people of different nationalities, social backgrounds, and economic classes, averaging 1 in about every 600 births. In the United States, over 400,000 people have the condition. Women over 35 are at greater risk of bearing a child with Down syndrome than younger women. One in 1500 children with Down syndrome is born to a mother under 30; for mothers over 45, this figure rises to one in 65. Altogether, though, 80% of all Down infants are actually born to women under 35. According to recent studies, the age of the father may play a role as well. Prenatal detection of Down syndrome is possible through amniocentesis and chorionic villus sampling and is recommended for pregnant women over the age of 35."

  • 1 decade ago

    The genetics of Down’s syndrome

    There are three types of Down’s syndrome:

    Standard (Regular or Primary) Trisomy 21

    About 94% of all people with Down’s syndrome fall into this group. This type of Down’s syndrome is always an accident of nature. It can happen to anyone and there is no known reason why it occurs. The parents have normal chromosomes, but the bay has three rather than two chromosome of the number 21 pair.

    Translocation

    This type of Down’s syndrome occurs in about 3% of babies with Down’s syndrome. Part of the number 21 chromosomes becomes attached to another chromosome so that both parts of the new large chromosome move together as one. In about half of the people who have Translocation Down’s syndrome, the translocation is a one-off occurrence and does not mean that it will happen again in any future pregnancies.

    In the other half, however, it occurs because one or other of the parent, though having a normal balanced chromosomal make-up, has one of the number 21’s ‘stuck on’ to another chromosome. In this case the chance of another child with Down’s syndrome being conceived is quite high. Blood tests can be carried out to find out more detailed information.

    Mosaicism

    This type of Down’s syndrome is also rare - only about 2-3 % of people with Down’s syndrome fall into this category. In Mosaic Down’s syndrome the cells with the extra 21 chromosome are mixed with other ‘normal’ cells. In other words, only a certain percentage of the cells are affected

    Source(s): I am a doctor.
  • 1 decade ago

    It's not a disease, it's a birth defect. When chromosome 21 has 3 parts instead of 2...also called Trisomy 21....there are 2 other kids....more rare...one is called mosaic Down's...in that case the 21st chromosome is in a LOT of pieces (like a mosaic). Because of this defective chromosome, people with Down's syndrome will have certain characteristics. They may not have all of them....for example, there are tall people w/ Down's as well as people that are NOT mentally retarded. A person could have all of the symptoms or just a few.

  • Google Down Syndrome. This is a genetic disorder. It DOES have a specific cause.

    Most people have 23 pairs of chromosomes, for a total of 46. But a baby with Down syndrome has an extra chromosome (47 instead of 46) or one chromosome has an extra part. This extra genetic material causes problems with the way their bodies develop.

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  • 1 decade ago

    most of the answers above are reliable concerning the chromosomes. however, I just wanted to add that it is not a disease...it is a genetic disorder. and there is a specific cause...an addition of an extra chromosome. the risks of having a child with DS increase with the mothers age. But it can also happen in woman of any age! I have met women as young as 16 yrs old who have a down syndrome child! it is a roll of the dice anyone can be the "1'' of 800 live births. did you also know that 80% of down syndrome babies are born to women under the age of 35 yrs old?? the reason this is, is because that is the age group that has the most babies.

    I just wanted to add...."walia" if you truely are a doctor, (which I highly doubt)...stick with research don't have patient contact because you lack compassion for the parents of the "defective" child! children with DS are just that...children! they may have slower development in certain areas, but they still are very capable of living 'typical' lives...they learn...they play....they love....they are wonderful children and when they grow up they are wonderful adults and add joy to the lives of those they meet...does that sound like a defective person to you?

    Source(s): mom to a little boy who happens to have down syndrome and he is the joy of my life!
  • 1 decade ago

    DOWN's syndrome is a genetic defect causing Mental Retardation and other defects in the child.

    Its strongly associated with mother's age and the risk increases as mother's age increases.

    During development of a gamete it has to divide such that out of 46 chromosomes present normally 23 are given to one cell and 23 to other. And finally when two sets of 23 chromosomes (1 each from male(sperm) and female(ovum) gamete) fuse, it leads to a Zygote (future embryo) with 23 pairs (=46) of chromosomes. Down syndrome occurs when the female gamete divides erroneously resulting in one ovum with 22 and other with 24 chromosomes, an extra 21st chromosome being retained in the latter. So now when this 24-chromosome-ovum fuses with a normal sperm it leads to a total of 47 chromosomes with the 21 chr being repeated thrice (1 from father(sperm) and 2 from mother(ovum)). It can be considered a miscalculation of sorts by Nature. Though nothing can be done to prevent it, thankfully, nowadays this can be diagnosed during pregnancy well in advance reliably, and the option of termination of pregnancy if it is found defective.

    Source(s): Me a doctor
  • 1 decade ago

    Its not a disease. Its a fault in the DNA. Google Down Syndrome and educate yourself on this condition.

  • 1 decade ago

    Down syndrom is a genetic mutation that happens at conception. It appears to happen more frequently when the mother is ofer 40 at the time of conception, but can happen with younger mothers also.

  • Anonymous
    1 decade ago

    Mosaicism is when some of the cells in the body have the extra chromosome and some don't because the abnormal cell division that produced the extra chromosome occured after conception.

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