Genetic engineering can modify any aspect of an organism, so long as the modification isnt something that causes the embryo to be unviable. It all depends on which genes are targeted. Phenotype is controlled by genes just like everything else
ya. ur changing the genetic code for that organism. the genetic code is how it is built. like for building a lego thing lets say. if u cross out part of the instructions and giv them 2 a gullable person, they will build the model differently