Final answer:
Most new mutations are neutral and do not affect an organism's fitness. Beneficial mutations are less common but can lead to adaptations that increase an organism’s chances of survival and reproduction. Detectability by protein electrophoresis and presence in homozygotes or heterozygotes are not defining characteristics of new mutations.
Step-by-step explanation:
The majority of new mutations are actually neutral; they do not affect an organism's ability to survive and reproduce. These include silent point mutations which do not change the amino acids in the proteins they encode. Beneficial mutations, though less common, lead to new versions of proteins that help organisms adapt to changes in their environment, and if they increase an organism’s fitness, they can become more common over time.
For example, the CCR5-4³² mutation confers HIV resistance. However, these mutations are relatively rare. Another important aspect is that mutations can be present in both homozygotes and heterozygotes, but this is not a defining characteristic of new mutations. Also, not all mutations can be detected using protein electrophoresis as this method only visualizes changes in protein structure or charge.