Science PowerPoint tips and tutorials

Another example where Curve Tool is especially useful is drawing of microRNA. Refer to Using Curve Tool to draw complex arrows, an apple and DNA, Essential Drawing Tools I and Setting up Your Personal Workspace and other previous articles for more information on how to use it and how to place this tools icon in the bottom drawing bar for your convenience.

Preparing template. In order to have the final object appear proportional and straight it is useful to draw the template first and use it as a guide for drawing with Curve Tool. First, draw circle and a straight horizontal line. Copy the line, rotate 90o and copy again. Assemble these objects as shown in Figure 44. You may add more lines and circles to further facilitate the drawing process.

Figure 44. Preparing template for drawing microRNA.

Drawing the stem-loop structure using Curve Tool. As shown in Figure 45, begin drawing the structure from the far left site and continue to the right site corner.

Figure 45. Steps for drawing the initial shape for stem-loop structure..

Editing the initial drawing. After you created a curved line resembling stem-loop structure a few editing steps are necessary to achieve the final shape. Use either Format AutoShape or Edit Points dialog boxes. Make sure that the line you are about to edit is highlighted - otherwise the corresponding dialog box will not be accessible with the right mouse button. More information on these menus is available from Using Curve Tool to draw complex arrows, an apple and DNA and Figures 38 & 39 therein. Within the Edit Points dialog box click on the line (segment) you want to transform and select the Straight Segment from the menu. In all, transform all six line segments that need to be straight. These steps are shown in Figure 46.

Figure 46. Editing the line shape using Edit Points dialog box.

Next, edit points within the curved segments of the stem-loop structure by clicking the right mouse button over the point to be edited, as shown in Figure 47

Figure 47. Editing points in the loop sections.

Select either smooth point or corner point and drag Bezier handles until desired curvature is achieved. To finish the stem-loop structure delete the template lines and circles, as shown in Figure 48, draw short horizontal line, copy it multiple times, align, distribute and position within the stem section to finish microRNA. Finally, you may also add text boxes with 7mG and AAAAAA at the beginning and at the end of the drawn line, respectively.

Figure 48. Addition of horizontal lines to complete the stem-loop structure.