Depends on parents. An unaffected mother or father could have a balanced(normal) set of chromasome material where a piece of one 21 chromasome is stuck on another.If the egg or sperm had the normal 21 and an extra 21piece hidden on another chromasome, they could pass it to the baby. It only takes an extra piece of 21 to cause ds.It is important to study ds to verify type, as translocation ds can recur each pregnany.
Yes. A woman with down syndrome (trisomy 21) may be able to get pregnant, but men with down syndrome are almost always sterile, due to problems with sperm production. That means about half of the babies born to women with down syndrome will inherit an extra chromosome #21 and be down syndrome babies. Said another way, if you inherited down syndrome, your mother must have had down syndrome.
Occurs at fertilizat. Down syndrome is a chromosome disorder in which an infant inherits 3 number 21 chromosomes. This occurs at fertilization. the extra chromosome is usually thought to be from the mother, but there are circumstances where it can be contributed by father. In rare cases, a portion of a 21 chromosome becomes attached to another chromosome, causing Down syndrome.