Two mutant lines of mice have been identified, each of which has a defect in T cell development. The subsets of thymocytes found in each mutant mouse line are shown in Figure

To narrow down the possible defects in each mutant line, a series of bone marrow chimeras are made in which bone marrow from one strain of mice (the ‘donor’ strain) is used to reconstitute a second strain (the ‘recipient’ strain), immediately following the irradiation of the recipient strain to eliminate its own hematopoietic cells. In this procedure, the resulting chimeras have hematopoietic cells that are 100% derived from the donor strain, and all other cells and tissues are derived from the recipient strain. The thymocyte profiles of the series of bone marrow chimeras is shown in Figure in each case the label at the top of each FACS plot refers to ‘donor bone marrow recipient’:

-A potential candidate molecule for the gene that is defective in Mutant-2 is:
A) CD4
B) MHC class II
C) Th-POK
D) MHC class I
E) Runx3

Question

Two mutant lines of mice have been identified, each of which has a defect in T cell development. The subsets of thymocytes found in each mutant mouse line are shown in Figure

To narrow down the possible defects in each mutant line, a series of bone marrow chimeras are made in which bone marrow from one strain of mice (the ‘donor’ strain) is used to reconstitute a second strain (the ‘recipient’ strain), immediately following the irradiation of the recipient strain to eliminate its own hematopoietic cells. In this procedure, the resulting chimeras have hematopoietic cells that are 100% derived from the donor strain, and all other cells and tissues are derived from the recipient strain. The thymocyte profiles of the series of bone marrow chimeras is shown in Figure  in each case the label at the top of each FACS plot refers to ‘donor bone marrow recipient’:

-A potential candidate molecule for the gene that is defective in Mutant-2 is:
A) CD4 
B) MHC class II 
C) Th-POK 
D) MHC class I 
E) Runx3

Quizplus · Accepted Answer

From the thymocyte profiles in the bone marrow chimeras, it is clear that Mutant-2 has a defect in the development of CD4+ T cells, as there is a complete absence of this subset in all chimeras with Mutant-2 bone marrow as the donor. Therefore, potential candidate molecules that may be defective in Mutant-2 should be involved in the differentiation of CD4+ T cells. Th-POK is a transcription factor that is required for the development of CD4+ T cells, and its absence leads to the development of CD8+ T cells instead. Thus Th-POK is the best choice for the potential candidate molecule for the gene that is defective in Mutant-2.

Two Mutant Lines of Mice Have Been Identified, Each of Which