Do the Twist!


DNA is an organic chemical of complex molecular structure found in all living cells; it codes genetic information allowing the transmission of inherited traits. The structure of DNA was determined in the 1950s as a double helix or twisted ladder.

Nucleotides are the DNA basic building blocks, and they are hooked together to form a chain. A nucleotide is composed of three components: sugar, phosphate, and a nitrogenous base. The sugar and phosphate constitute the backbone of the DNA double helix, while the bases are located in the center. It is the chemical bonds between the bases that hold the two strands of the twisted ladder together.

Bases store information and give DNA the ability to encode an organism’s traits; there are four bases: Adenine (A), Cytosine (C), Guanine (G), and Thymine (T). Adenine always binds to thymine, while cytosine and guanine always bind to one another; these bonds break when the DNA unzips and duplicates itself.

Now, follow the following steps to make your own 3-D model of DNA.

Required material

  • Pencil
  • Ruler
  • Colored thick paper
  • Four coloring markers
  • Adhesive tape
  • Scissors
  • Toothpicks.


  • Use the scissors to cut two strips of colored paper that are at least 60 cm long and about 3 cm wide.
  • Use the pencil and ruler to mark each 2.5 cm along each strip.
  • Choose four colors from your markers to represent the four DNA bases: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).
  • Take 10 toothpicks. For each one, color half the toothpick the color you chose for A, and color the other half the color you chose for T.
  • Take 10 more toothpicks and do the same with the colors you chose for C and G.
  • Grab both strips of paper, put one on top of the other, and tape them together at each end.
  • Poke a toothpick through the center of the strips using the pencil marks as a guide.
  • Keep going until your strips are filled up, and make sure all the toothpicks are pushed halfway through the holes.
  • Gently spread the two strips apart until your model looks like a ladder.
  • Carefully twist the ladder at least once around until it looks like a double spiral.


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SCIplanet is a bilingual edutainment science magazine published by the Bibliotheca Alexandrina Planetarium Science Center and developed by the Cultural Outreach Publications Unit ...
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