Final answer:
The irradiated mouse injected with progenitor cells from a healthy matched donor will likely live a long and healthy life with a steady supply of differentiated blood cells; the key is matching the donor to prevent immune rejection.
Step-by-step explanation:
When a graduate student uses x-irradiation to halt blood cell production in a mouse and then injects isolated committed progenitor cells from a healthy donor into the irradiated mouse's bone marrow, the most likely observation will be answer choice b) the irradiated mouse will live a long and healthy life, with a steady supply of committed progenitor and differentiated blood cells. This is because x-irradiation is used to eradicate the recipient's own bone marrow cells, making way for the donor's healthy progenitor cells to repopulate the marrow. Given that the donor cells are matched to prevent immune rejection, the newly injected cells should be able to differentiate and replenish the blood cell population, assuming no complications arise.
It is important that a matching donor is found to ensure the immune system does not destroy these newly introduced cells. The injected progenitor cells will establish themselves in the recipient's bone marrow and will continuously differentiate into mature blood cells to replace those that were lost due to irradiation or natural cell turnover.