Question
At what phase is the cell cycle arrested by an inhibitor?
One potential medical treatment to stop cancer cell proliferation employs an inhibitor derived from human umbilical cord stem cells. In this exercise, you will compare two histograms to determine where in the cell cycle the inhibitor blocks the division of cancer cells.
In the treated sample, human glioblastoma (brain cancer) cells were grown in tissue culture in the presence of inhibitor-producing umbilical cord stem cells. In contrast, control sample glioblastoma cells were grown in the absence of stem cells. To get a “snapshot” of the phase of the cell cycle each cell was in at the end of 72 hours, the cell samples were treated with a fluorescent chemical that binds to DNA. Next the samples were run through a flow cytometer, an instrument that records the fluorescence level of each cell. Computer software then graphed the number of cells in each sample with a particular fluorescence level.
Part A - Identifying the control and the treatment
What treatment is being compared to the control in the experiment?
The treated glioblastoma cells were stained with a fluorescent dye, but the control cells were not stained.
The treated glioblastoma cells were cultured in the presence of an inhibitor from umbilical cord stem cells, but the control cells were cultured without the inhibitor.
The control glioblastoma cells were run through the flow cytometer and then treated by being cultured in the presence of an inhibitor.
The treated umbilical cord stem cells were cultured in the presence of an inhibitor from glioblastoma cells, but the control cells were cultured without the inhibitor.
Request Answer
Part B - Reading the histograms
The data are plotted in a type of graph called a histogram, which groups values for a numeric variable on the x-axis into intervals. A histogram allows you to see how an entire group of experimental subjects (cells, in this case) are distributed along a continuous variable (amount of fluorescence). In these histograms, the bars are so narrow that the data appear to follow a curve for which you can detect peaks and dips. Each bar represents the number of cells observed to have a fluorescence level in that interval. This in turn indicates the relative amount of DNA in those cells.
Which axis indirectly shows the relative amount of DNA per cell? By what relationship?
The x-axis; the DNA was stained, so there is a positive correlation between fluorescence and DNA content.
The y-axis; the DNA was stained, so there is a positive correlation between fluorescence and DNA content.
The y-axis; DNA content was the dependent variable.
The x-axis; the DNA is naturally fluorescent so there is a positive correlation between fluorescence and DNA content.
One potential medical treatment to stop cancer cell proliferation employs an inhibitor derived from human umbilical cord stem cells. In this exercise, you will compare two histograms to determine where in the cell cycle the inhibitor blocks the division of cancer cells.
In the treated sample, human glioblastoma (brain cancer) cells were grown in tissue culture in the presence of inhibitor-producing umbilical cord stem cells. In contrast, control sample glioblastoma cells were grown in the absence of stem cells. To get a “snapshot” of the phase of the cell cycle each cell was in at the end of 72 hours, the cell samples were treated with a fluorescent chemical that binds to DNA. Next the samples were run through a flow cytometer, an instrument that records the fluorescence level of each cell. Computer software then graphed the number of cells in each sample with a particular fluorescence level.
Part A - Identifying the control and the treatment
What treatment is being compared to the control in the experiment?
The treated glioblastoma cells were stained with a fluorescent dye, but the control cells were not stained.
The treated glioblastoma cells were cultured in the presence of an inhibitor from umbilical cord stem cells, but the control cells were cultured without the inhibitor.
The control glioblastoma cells were run through the flow cytometer and then treated by being cultured in the presence of an inhibitor.
The treated umbilical cord stem cells were cultured in the presence of an inhibitor from glioblastoma cells, but the control cells were cultured without the inhibitor.
Request Answer
Part B - Reading the histograms
The data are plotted in a type of graph called a histogram, which groups values for a numeric variable on the x-axis into intervals. A histogram allows you to see how an entire group of experimental subjects (cells, in this case) are distributed along a continuous variable (amount of fluorescence). In these histograms, the bars are so narrow that the data appear to follow a curve for which you can detect peaks and dips. Each bar represents the number of cells observed to have a fluorescence level in that interval. This in turn indicates the relative amount of DNA in those cells.
Which axis indirectly shows the relative amount of DNA per cell? By what relationship?
The x-axis; the DNA was stained, so there is a positive correlation between fluorescence and DNA content.
The y-axis; the DNA was stained, so there is a positive correlation between fluorescence and DNA content.
The y-axis; DNA content was the dependent variable.
The x-axis; the DNA is naturally fluorescent so there is a positive correlation between fluorescence and DNA content.
Answers
GPT-4o mini
**Part A - Identifying the control and the treatment**
The correct statement regarding the treatment being compared to the control in the experiment is:
**The treated glioblastoma cells were cultured in the presence of an inhibitor from umbilical cord stem cells, but the control cells were cultured without the inhibitor.**
---
**Part B - Reading the histograms**
The correct interpretation of which axis indirectly shows the relative amount of DNA per cell is:
**The x-axis; the DNA was stained, so there is a positive correlation between fluorescence and DNA content.**
This is because the x-axis represents the levels of fluorescence, which corresponds to the amount of DNA in the cells that were stained. Hence, as the fluorescence increases, it indicates a higher DNA content.
The correct statement regarding the treatment being compared to the control in the experiment is:
**The treated glioblastoma cells were cultured in the presence of an inhibitor from umbilical cord stem cells, but the control cells were cultured without the inhibitor.**
---
**Part B - Reading the histograms**
The correct interpretation of which axis indirectly shows the relative amount of DNA per cell is:
**The x-axis; the DNA was stained, so there is a positive correlation between fluorescence and DNA content.**
This is because the x-axis represents the levels of fluorescence, which corresponds to the amount of DNA in the cells that were stained. Hence, as the fluorescence increases, it indicates a higher DNA content.