Down syndrome is caused by nondisjunction of chromosome pair 21. If a person with Down syndrome has a child with a person who does not have Down syndrome, what is the probability that the child will have Down syndrome?

25%
50%
75%
100%

Question

Down syndrome is caused by nondisjunction of chromosome pair 21. If a person with Down syndrome has a child with a person who does not have Down syndrome, what is the probability that the child will have Down syndrome?




   25% 
   50% 
   75% 
   100%

anonymous · Answer

50% because the disjunction may happen in any sex cell that is undergoing cell division, but does not have to happen necessarily and its not a heritable trait.