b. False
DNA mutations occur in the genetic material of an organism, specifically in the DNA sequence. The shape of the extracellular portion of a protein is determined by the amino acid sequence of the protein, which is encoded by the DNA. A change in the DNA sequence can result in a change in the amino acid sequence and therefore the shape of the protein, but the mutation would be located in the DNA, not in the extracellular portion of the protein.
It's important to note that a change in the shape of extracellular portion of a protein, can have various effects on the protein activity, stability, and interactions with other molecules, but the change would occur after the protein is translated from the DNA, not in the DNA itself.