An organ transplant between two genetically non-identical individuals of the same species is classified as an Allograft. In the provided scenario, a mother donating a kidney to her son involves individuals who are genetically different but belong to the same species. Therefore, this transplant type is considered an allograft. The other options are defined as follows:
- Isograft: A transplant between genetically identical individuals, such as identical twins.
- Autograft: A transplant where the donor and recipient are the same person, such as a skin graft.
- Xenograft: A transplant between members of different species, such as pig heart valves used in humans.