Is triple-strands or multiple-strands DNA possible?

It is possible but impractical.

Double-helix DNA's structure is something like this:

$$ \text{B "” (A/C/T/G) : (T/G/A/C) "” B} $$

where B is a backbone molecule, A/C/T/G is adenine/cytosine/thymine/guanine, "” is a molecular bond, and : is a hydrogen intermolecular bond.

What's important here is the molecule connecting the strands: since it's only connecting 2 backbones, it's a relatively simple molecule.

3-way DNA I can't accurately represent with MathJax, so here's a picture:

In this diagram, a line is a molecular bond, a dotted line is a hydrogen intermolecular bond, B remains the same, H and N are hydrogen and nitrogen, and (AF/CF/TF/GF) is some variation of (A/C/T/G) where the molecule must incorporate a fluorine molecule on the outside of the molecule.

The part in the center is $\text{NH}_3$, which I have picked purely because it has 3 outer hydrogen molecules. These hydrogens form hydrogen intermolecular bonds with the fluorine atoms in (AF/CF/TF/GF).

There are relatively few 3-way molecules like $\text{NH}_3$, so 3-way DNA is more difficult and more fragile than 2-way.

4-way DNA is also possible: substitute $\text{NH}_3$ in the diagram for $\text{CH}_4$, methane, which has 4 outer hydrogens and can thus form intermolecular bonds with 4 (AF/CF/TF/GF) - B groups.

The major point to note here is that DNA is the way it is because it's simple: 2-way DNA does not require another molecule in the middle like my representations of 3- and 4-way DNA do. While my ideas are probably not optimal, 2-way DNA is both simpler and stronger than any other type.

(Also, DNA helicase (one of the enzymes that process DNA) would have a hard time adapting for 3- or 4-way DNA.)

posted over 9 years ago

ArtOfCode‭ staff

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