Prader-Willi syndrome is caused by a missing gene on chromosome 15. Normally, parents each pass down a copy of this chromosome. The defect can occur in a couple of ways: The father's genes are missing on chromosome 15; There are defects or problems with the fatherâs genes on chromosome 15
poison meaning, definition, what is poison: a substance that can make people or animals ill or kill them if they eat or drink it: . Learn more.
  poisonous means that it is harmful if eaten, breathed in or  touched, you â¦ could safely eat any snake (even the venomous ones)  and not become ill.    venomous means they inject enzymes (venom) to subdue their prey.    here is a list of the top 10 most venomous snakes.