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

question 12

Multiple Choice

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-1 is:

• A) CD4
• B) MHC class II
• C) Th-POK
• D) MHC class I
• E) Runx3

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Definitions:

Vertebrae

The series of small bones forming the backbone, protecting the spinal cord and supporting the body.

Ligament

A short band of tough, flexible, fibrous connective tissue that connects two bones or cartilages or holds together a joint.

Cranial Suture

A fibrous joint that connects the bones of the skull, allowing for growth during infancy and becoming less distinct in adulthood.

Endosteum

A thin vascular membrane of connective tissue that lines the inner surface of bony tissue that forms the medullary cavity of long bones.