Explain how a child can have a different phenotypic characteristic that neither parent has

You are lucky because I just finished learning this! 

See a child or offspring that shows a dominant trait that is not shown in parents can be recessive for either one or both parents. So basically one or both parents might have a recessive trait that showed up in the offspring! 

Organism, organ system, organs, tissue, cells

The basic repeating unit of nucleic acids are known as nucleotides. a nucleotide consists of three distinct chemical groups.