Doctor insights on:
Mode Of Inheritance Of Down Syndrome
There is none: You do not inherit ds from your parents in the traditional dominant or recessive fashion. During formation of the egg, only one of a pair of the 23 separate chromosomes is present so the sperm bringing 23 will reestablish the 46. Ds occurs when an extra 21 (or piece of a 21) is present in the egg after conception. This is a chromosome number change, not an inherited trait. ...Read more
Down syndrome is a genetic condition in which there is an extra chromosome present. Symptoms may range from mild to severe. Children with Down syndrome share a common physical appearance including a flattened nose, small ears, a small mouth, upward slanting eyes, and a single crease in the ...Read more
Is down syndrome dominant , recessive , polygenic inheritance , multiple alleles , sex linked, codominance , or incomplete dominance ?
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. ...Read moreSee 2 more doctor answers
If someone in your family has down syndrome, is there a larger risk that your baby will have down syndrome?
Slight risk: Most down syndrome is sporadic. A few patients with down syndrome have the extra 21 chromosome translocated on to another chromosome. In some of these cases the parents can carry the translocated chromosome in a balanced form and they and other family members could be at increased risk to have children with the syndrome. ...Read moreSee 2 more doctor answers
Chromosome defect: Ds is one of the more common chromosome(c) defects that can survive pregnancy (many others miscarry).Eggs are supposed to have a single 21c & combine with the 21 from dads normal sperm.Here a pair of moms 21c +dad's 21 creates a baby with the extra 21c in all tissues.This extra material confuses the creation of body parts causing ds..Various prenatal tests can pick up signs early on. ...Read more
1/100 births: As above the rate of ds births are lowest in the early 20's at about 1/2000 with a gradual increase in risks that hit 1/100 at 40.There is always a baseline risk of about 4% of an unexpected outcome with any pregnancy.This must be added to specific age related risk. A visit with a genetic counselor can identify specific risk for any couple. ...Read more
1 in 700: Approximately 1 in 700 births is affected with downs syndrome. This incidence increases with advancing maternal age. ...Read more
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