Final answer:
Frog oocytes are useful for studying transporters, but they do not inherently express all known transporters; they are beneficial because they can express injected heterologous mRNAs. They are also large, easily injectable, inexpensive, and can be maintained in minimal conditions. They are particularly suitable for embryonic development studies and cloning research.
Step-by-step explanation:
The student's question centers around the characteristics of frog oocytes that make them a useful experimental system for studying transporters. The characteristic that frog oocytes do not possess is (B) they express all transporters known. While frog oocytes can indeed be easily injected (A), are relatively inexpensive and easy to obtain (D), and can be maintained in simple conditions (E), they do not inherently express all known transporters. Instead, they are valuable because they can express injected heterologous mRNAs (C), which allows researchers to introduce specific transporters into the cells for study.
Frog oocytes, especially from the African clawed frog, Xenopus laevis, are substantial in size and thus fairly easy to manipulate, which is ideal for investigations involving microinjection of substances like mRNAs. They are commonly used for studying various biological processes, including embryonic development and the function of proteins at specific stages. This is possible because the developmental stages of the frogs after fertilization can be precisely determined due to the clear visibility and size of the embryos.
Furthermore, the study of embryonic development is facilitated in amphibian species, such as frogs, due to their shell-less eggs. These characteristics make them an excellent model for various studies, including cloning research, where large egg size is beneficial.