How can a genotype change a phenotype?

Answer:
The existence of [any and all] phenotypes directly results from the Expression of All of the Genes that are responsible for the physical implementation of that phenotype.

Most (see Wobble base pairs) changes in the genetic sequence of the organism's chromosomes - it's genotype - will also cause changes in it's phenotype.
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First answer by Betaclamp. Last edit by Betaclamp. Contributor trust: 104 [recommend contributor recommended]. Question popularity: 6 [recommend question].