ing
Forum Guru
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95% Trisomy 21, cause is maternal meiotic nondisjunction. There are 3 21st chr in each cell. It is related to maternal age.
4% caused by robertsonian translocation. It is between 21st chr and another chr, which is usually 14th. The number of chr is normal, but since some of 14th chr is replaced by 21st chr, each cell has triplication of 21st chr material. (I guess it must be 3 21st chr at begining, then the extra 21st chr translocate to another chr. Please correct me if I'm wrong)
1% mosaicism. Some cells have trisomy 21, others have a normal set chr.
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| ing
Forum Guru
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Oh, never mind. I just figured out for those 4% caused by translocation, it doesn't need to have tri 21st chr at the begaining. After translocation, the next generation cells will have three chromosomes carrying 21st chr material. :-)
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| K1
Forum Senior
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60 year old female with down facies and normal intelectual development. Which of the above mechanisms can be responsible for that?
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| cyra
Moderator
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Mosaicism would be responsible.
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| ing
Forum Guru
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agree, mosaicism.
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| K1
Forum Senior
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You are right . I saw a case like this 1 year ago. And one of my students asked me why didn't she developed Alzheimer's disease. because we all know that Down patients surviving untill their 40's usually develop this type of dementia.
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| K1
Forum Senior
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Mother brings her 4 months old baby with a down facies because of vomiting. The vomitus usually has a yellow color and is non projectile. The baby is small for age, sleepy, with a depressed anterior fontanelle.
What is the most common diagnosis?
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| msyamp
Forum Fanatic
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duodenal atresia
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