Over the holidays I carved out some time in my beading schedule to treat myself to a new jewelry set. It's another piece of
beaded DNA, in the Y-shaped structure of a
replication fork.
The colors and design of the necklace came about from a pair of earrings that I made alongside several
other pairs of earrings that I wove for Christmas presents. For this pair, I continued the theme of using larger beads for the purines and smaller beads for the pyrimidines: I used 4 mm bicone crystals for A and G, and 3 mm bicones for C and T. I also added little caps at both ends of the earrings for an aesthetic effect.
The problem with these earrings is that I didn't use a seed bead between the crystals and the DNA backbone, which leaves the thread exiting the crystal at an angle. As any experienced beader will tell you, this can make the thread weaken and snap, which was the case when I made these earrings even though I used the stronger fireline thread instead of a nylon thread. As such, I didn't feel comfortable giving away or selling these earrings, so I kept them for myself.
These earrings needed a matching necklace, so I set out to create a beaded replication fork. For the types of beads used in the DNA itself, I added back in a 15° seed bead between the crystals and the backbone, so that the necklace would be stronger than the earrings. I also decided to forego the variation that yields
major and minor grooves that you can see in my
gene regulation necklace. The resulting necklace less-accurately portrays real DNA in that respect, but it does look closer to real DNA in another; since I used smaller beads for the backbone (I replaced some of the 11° seed beads with 15° seed beads, and the 8° seed beads with 11° seed beads), and a relatively longer set of beads for the base pairs (approx. 9 mm), there are about 11 base pairs per turn of the beaded double helix. B-DNA has about
10.5 base pairs per turn. In all the variations I've beaded on this design, I've only been able to get up to about 8 base pairs per turn until now. (For more on this subject, take a look at Gwen's two
crystal DNA pieces - you can really see the effect of base pair length on helical pitch in these pieces).
I call this necklace a
replication fork because it depicts how real DNA is replicated; since each base pair is defined (C always pairs with G and A always pairs with T), each strand has enough information to serve as a template for the other strand. Real DNA replicates this way; the double helix is unwound into single strands, and the new strands are synthesized on to the two older strands, one nucleotide at a time. So in this piece, the older DNA is at the focal point of the necklace, and the newer DNA wraps up the necklace towards the back.
For the branch point of the necklace, I left one base pair unpaired so that each daughter strand had enough room to twist up the necklace. I should note that a real DNA replication fork looks quite different than this one; the two new strands are not joined together at the branch point as they are in this necklace, and there are quite a few more bases unpaired at the branch point. The method of replication is also different for each of the two strands because of the antiparallel nature of the strands and the requirement that DNA can only be synthesized in one direction, but that's a story for another time.
The necklace has a beaded custom toggle clasp, woven with a twist on the embellished RAW technique.
Finally, additional Swarovski bicone crystals and Venetian glass rounds complete the necklace.
The sequence used in this necklace comes from the alpha subunit gene of the
E. coli DNA polymerase III complex, which is responsible for most of the DNA synthesis in the
E. coli cell. The story of its discovery, 24 years after the
first DNA polymerase was characterized, is an interesting lesson in persistence and the methodology needed to solve complicated scientific questions. Plus it's the perfect sequence to use for a depiction of DNA replication :)
