If you imagine your DNA right now. You’d probably picture that double helix you learned
about in school at some point- hopefully. But, it may actually look a lot different.
Hey guys I’m Sapna here at DNews. That ladder twisted on itself with bonds between 4 bases-
adenine guanine thymine and cytosine, that is the DNA double helix. The thing you were
probably picturing in your head. But it’s now thought DNA, at times, may have different
configurations. The helix can twist the other way, have a couple extra strands- it can even
twist onto itself into some pretty cool shapes.
There are 3 biologically active types of the double helix- a , b and z. B-DNA is that recognizable
one, it has a right handed twist and it’s the most common in living cells. *(it’s
in yours, dogs, flowers). A-DNA has a wider spiral… and Z-DNA twists the other way,
it’s a left handed double helix with a zig zag structure. The biological purpose of Z-DNA
isn’t quite clear. Since it twists the other way it’s thought to relieve some of the
torsional stress on the structure. And some research shows it may play a role in transcription-
where the genetic info is being copied.
Beyond the double helix- new research says DNA molecules may also coil into a range of
cool shapes called supercoils. Research published in the journal Nature Communications last
October shows images of supercoiled DNA created by cryo-electron tomography together with
supercomputer simulations. The scientists wanted to know how all that DNA crams itself
into a tiny nucleus. So they tried to look at it one twist and turn at a time. They found
sharp bends, figure 8s- even coils that looked like handcuffs. Keep in mind this research-
like most of the research on DNA- is in vitro or in the laboratory. But by using an enzyme
called human topoisomerase II alpha, they did try to simulate conditions in the human
body to show that supercoiled DNA is possible.
So your DNA may be backwards, or zig zagged or even twisted. But, it might also have double
the strands!
Most DNA has 2 strands, but many people don’t know it can also have 4. It’s called G-
Quadraplex DNA or G4 DNA. The "G" refers to guanine, one of those four bases that holds
the DNA together and spells out our genetic code. G4 DNA is a topic that scientists are
trying to learn more about, especially in the last decade because it may hold the key
to some major medical breakthroughs.
Researchers in Sweden just recently discovered G4 DNA in one species of yeast. They published
their findings in the journal Nucleic Acids Research. Meanwhile a team led by Florida
State Researchers looked for and found G4 DNA in the genome of the maize, or corn, plant.
And in 2012 Cambridge University researchers claim they saw G4 DNA in human cells. Using
a fluorscence biomarker, they tagged an antibody they created to specifically look for the
4 strand DNA in human cells and and bind to it. They found that the G4 DNA seems to turn
up most often (during the S- phase*)… just before cells are about to divide.
Which brings us to the point of why we should care about 4 stranded quadriplex G4 DNA? If
it plays a role in cell division, either speeding it up or slowing it down. Scientists think
G4 DNA may play a role in causing cancer and degenerative diseases in humans.
So how do you turn it on or off? And is possible to create a drug that targets 4 strand DNA
and… maybe.. stop cancer? We’re not there yet but that is actually a goal and focus
for ongoing research.
By the way have you ever heard someone say “I love to travel! It’s in my DNA!”
Is it true? Are some of us hardwired for wanderlust? Watch this video by Julian to find out.
So what do you guys think about 4 strand DNA? And do you have any other science questions
you want to know more about?
Tell us in the comments section down below! And don’t forget click subscribe for new
episodes every day. I’ll see you next time on DNews.