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:

High-power

Refers to an objective lens on a microscope with a high magnification capability, used for examining small or detailed samples.

Iris Diaphragm

It is an adjustable aperture in optical devices, like microscopes and cameras, controlling the amount of light passing through the lens.

Revolving Nosepiece

A rotating part of a microscope that holds the objectives, allowing for quick changing of magnification by rotating the objectives into position.

Substage Light

A light source located beneath the stage of a microscope that illuminates the specimen from below, enhancing its visibility.