First, we need to recognize each strand, the original one and the complementary one. We can recognize the original strand because bases are already given. So,

The original strand is the one at the left,
The complementary strand is the one at the right.

Now we need to recognize and pair the bases. Names are written with their letters.

Nitrogenated bases that form nucleic acids correspond to purines and pyrimidines. Adenine and guanine derive from purines, while Thymine and Citocine derive from Pyrimidines.

In the DNA molecule, Adenine (Purine) forms pairs with Timine (Pyrimidine), while Guanine (Purin) pairs with Cytosine. Two hydrogen bonds join the A-T pair, and three hydrogen bonds join the G-C.

Once we drag the base labels to their targets, we need to recognize each of the strain extremes.

One of the extremes has a phosphate group, which is named 5´. The other extreme has a hydroxyl OH named 3´. Both of them are readen in the 5´to 3´ direction. The polymerase enzyme reads the original strand in 5´ to 3´ mode, and the molecule lecture goes from 3´to 5´.

So, by looking at the labels, we will recognize the phosphate extreme and the hydroxyl one. We will place in the superior extreme of the original strain the phosphate group 5´ and in the other extreme the OH 3´. These positions will give us the direction reflected by the arrow. The complementary strand will have the same extreme labels but in opposite places. So first we will place the OH 3´ label in the superior extreme, and the phosphate 5´label in the inferior extreme, defining the direction reflected by the arrow.

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3 years ago