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IB Biology SL B2.3.3 Stem Cell Niches in Adult Humans Questions

Explore how adult bone-marrow niche signals regulate haematopoietic stem-cell retention and mobilization in IB Biology SL B2.3.3.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam points

  • Interpret treatment-response data to compare bone-marrow stem-cell release after isoprenaline and clenbuterol with the control.
  • Compare CXCL12 mRNA levels after isoprenaline and clenbuterol with the control.

IB Biology SL B2.3.3 Stem Cell Niches in Adult Humans Questions question 1

[Maximum number: 3]

Stem cells in the bone marrow can be forced into blood vessels in a process called mobilization. Mobilization of stem cells from the bone marrow into the blood vessels represents the basis for modern bone marrow transplantation procedures.

To test the effect of light on the mobilization of stem cells, mice were subjected to a simulated "jet lag" by advancing the light-dark cycle by 12 hours. This was done by subjecting mice to a 24-hour light period before the results shown in the graph were recorded. The results were compared to the stem cells in control mice under normal conditions of 12 hours of light (□) and 12 hours of darkness (dark box).

Graph key: diamonds joined by a solid line represent Control; triangles joined by a dashed line represent Jet lag.
Time-series graph of stem cells per millilitre of mouse blood over 2–38 hours, comparing control and jet-lag conditions. Two strips below show light as white and darkness as black for the corresponding schedules.

Compare the effect of isoprenaline and clenbuterol with the normal release of stem cells and the production of mRNA for CXCL12.

Opposing horizontal bars for control, isoprenaline and clenbuterol treatments. Bars left of zero show CXCL12 mRNA as a percentage of control; hatched bars right of zero show stem cells released.
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