The numerical scales on both figures A and B are appropriate and the Y-axis labels are complete. However, the X-axis should be labelled with the units (in this case μM). Error bars are necessary (and included here) as each data value represents the mean of three experiments.
The figure legend includes a number, title, and brief descriptions of the methods used as well as the main trends observed in the data presented. This is a good legend. It contains sufficient detail for the reader to understand the figure without reference to the main article and it is concisely written.
The lines on the graph are presented in colour. If this figure is prepared for publication in a journal, then it would be reproduced in black and white to minimise the cost of publication. Therefore, the use of coloured lines would be inappropriate and instead the author should use black lines.
The figures are labelled A and B but there is no mention of A and B in the legend. A is clearly oxaliplatin treatment and B is etoposide treatment as explained by the keys placed in the body of the figure. Therefore, the inclusion of A and B labels in this instance is unnecessary.
A main shortcoming of this figure is that the two data lines are presented on two separate graphs when clearly the effects of treatment are being compared against each other. This makes the latter part of the statement "The proportion of apoptotic cells increases with increasing concentrations of both DNA-damaging agents but is higher with oxaliplatin treatment than with etoposide treatment" difficult to visualize. The two lines should be presented on a single graph to ease comparison of trends.
The two separate graphs could be re-designed as below. If you study the re-designed graph you will see that coloured lines are not used but replaced by black lines of different weights. In addition, each axis is labelled completely with labels and units.
Figure 4: Effect of DNA-damaging agents on cell viability of colon cancer cells. Colon carcinoma cell line HCT-116 was treated with DNA-damaging agents, oxaliplatin (50μM) or etoposide at a range of concentrations (0, 10, 20, 30, 40, 50, 60, 70μM) for 24 hours. Apoptotic cell death was measured using the Annexin V assay. Data represents the mean (± SEM) of three independent experiments. The proportion of apoptotic cells increases with increasing concentrations of both DNA-damaging agents but is higher with oxaliplatin treatment than with etoposide treatment.
