Question 1
Paper 2Medium16 marksAdult human bone-marrow stem cells were divided into equal groups of 100 cells. Each group was exposed for seven days to a different set of signals, M or N, from bone-marrow niche cells. Assume that no cells died, differentiated cells did not divide, and all cells present at day 7 were either stem cells or newly differentiated blood cells.
| Signal condition | Stem cells at day 7 | Newly differentiated blood cells at day 7 |
|---|---|---|
| M | 240 | 60 |
| N | 60 | 240 |
State two properties of stem cells.
Name two adult human locations that contain stem-cell niches, and state one role of a niche.
Calculate the percentage of counted cells that were stem cells in condition M and condition N.
Compare the outcomes for M and N and infer which set of signals favoured maintenance or proliferation of the stem-cell population and which favoured differentiation.
A researcher concludes that these results prove that the stem cells can divide endlessly and differentiate along different pathways. Evaluate this conclusion using the data.