Strawbees are becoming the latest rage in tinkering and making. You can form remarkably complex structures with deceptively simple connectors.

Concept

Use Strawbees to model deoxyribonucleic acid (DNA)

Required Materials

Full length straws (100%) - 12

¾ length straws (75%) - 4

½ length straws (50%) - 14

¼ length straws (25%) - 14

3-leg Strawbees - 4

2-leg Strawbees - 27

1-leg Strawbees - 25

Small lock-ring Strawbees - 8

Step 1: Building the Base Structure

Base square *3-leg (4), 1-leg (4), small lock ring (8), full length straws (4)*

Use the 3-leg Strawbees and 4 full length straws to form a square base with the spare leg on the Strawbees pointing upward. Use the 8 lock rings to secure the straws by sliding two onto each straw, pressing each lock ring onto each spoke until it rests in the notch. Place a 1-leg through the center hole of each of the 3-legs pointing to the center of the square, pressing each 1-leg to the base of the spoke.

Center hub *2-leg (2), 1-leg (3), ¼ length straws (2), ¾ length straws (4), full length straws (1)*

Place two 2-leg Strawbees perpendicular to each other on the spoke of a 1-leg Strawbee, press the crossed 2-legs all the way to the base of the 1-leg spoke. Attach the ¾ length straws to the four spokes of the 2-legs. Orient the hub in the center of the square with the center 1-leg spoke pointing upward. Loosely place a 1-leg each on two of the hub straws opposite each other. Press a ¼ length straw onto these two 1-legs. Secure the other end of the four hub straws to the 1-leg spokes at the corners of the base square. Attach the full length straw to the 1-leg in the center of the hub.

Step 2: Lower Helix

Ladder rungs (each)*2-leg (3), 1-leg (2), ½ length straws (2), ¼ length straws (2)*

Press the ½ length straws onto both ends of a 2-leg. Press each of the remaining 2-legs to the base of the spoke of a 1-leg. Attach the 1-leg spoke to the open end of the ½ length straws. Slide the ladder onto base support’s center hub through the central 2-leg. Attach the outer 2-legs to the open end of the ¼ length straws loosely connected to the central hub support beams (or level below for successive strands). Press new ¼ length straws onto the other end of the outer 2-legs for attaching to the next level up. Repeat this process until you have three (3) full ladder strands. At this point the three ladder rungs should be resting in a fairly straight ladder supported by the central hub. Now we need to start the helical twist.

Helix*2-leg (2), 1-leg (2), full length straws (6)*

Press a 1-leg through each 1-leg on the third rung of the ladder, making sure it points downward and is pressed all the way in to the base of the spoke. Attach two full length straws to the downward pointing 1-legs. Attach the other end of these straws to the bas e corners that do NOT have a beam directly supporting the outside of the ladder, this will cause the ladder to twist. Assemble the remaining full length straws and 2-legs and attach them to the other two corners of the base. These will be used in the next step to support the upper portion of the ladder.

Step 3: Upper Helix

Center hub*2-leg (1), full length straw (1)*
Assemble the 2-leg and full length straw, and press onto the existing center hub.

Ladder rung (each)*2-leg (3), 1-leg (2), ½ length straws (2), ¼ length straws (2)*

Press the ½ length straws onto both ends of a 2-leg. Press each of the remaining 2-legs to the base of the spoke of a 1-leg. Attach the 1-leg spoke to the open end of the ½ length straws. Slide the ladder onto base support’s center hub through the central 2-leg. Attach the outer 2-legs to the open end of the ¼ length straws from the level below it. Press new ¼ length straws onto the other end of the outer 2-legs for attaching to the next level up. Repeat this process until you have four (4) full ladder strands.

Helix*1-leg (2)*

Press a 1-leg through each 1-leg on the top rung of the ladder, making sure it points downward and is pressed all the way in to the base of the spoke. Attach these to the base square’s double full length straw assemblies you got ready in the previous step. You should need to continue the helical twist to connect these supports.

Step 4: Improving the Model

Expanding the Helix

You can expand the helix by replacing the 1-legs on the outer support arms with 2-legs. You can then use the same pattern and direction to build up the helix. Remember that the outer support arms and the inner helix twist in opposite directions from each other.

Doubling the Helix

You can double the helix by doubling the amount of ladder strands you make and alternating them between the existing helix ladder strands. This new helix would attach to the free outer support arms perpendicular to the existing helix. Make sure you twist the second helix in the same direction as the first.

Adding Color
Instead of the clear straws I used, get straws in five (5) other colors. Use the clear for the base, hub, and outer supports. Use one color for the ¼ length straws in the helical bands. Use the remaining colors to color code the ½ length straws for each of the four nucleobases; cytosine (C), guanine (G), adenine (A), and thymine (T).