A chromosome.
A hereditary unit consisting of a sequence of DNA that occupies a specific location on a chromosome and determines a particular characteristic in an organism. Genes undergo mutation when their DNA sequence changes.
For apex it's "A piece of a chromosome."
Nope, the alleles for smile dimples are actually dominant, not recessive.
Asexual reproduction results in offspring which are genetically the same as the parent organism (not counting a rare mutation). Sexual reproduction produces a random mixture of the genetics derived from both parents.
In sexual reproduction, offspring are not identical to either parent.
Any mutation could do so.