Kind: captions
Language: en
these are tiny molecular machines and
they are doing this inside your body
right now to understand why we have to
zoom out everyday in an adult human body
50 to 70 billion of your cells die
either they're stressed or damaged or
just old but this is normal in fact it's
called programmed cell death but to make
up for all these lost cells right now
billions of your cells are dividing
essentially creating new cells and that
process of cell division also called
mitosis well it requires an army of tiny
molecular machines so let's take a
closer look
DNA is a good place to start the double
helix molecule we always talk about this
is a scientifically accurate depiction
of DNA created by drew Berry at the
Walter and Eliza Hall Institute of
medical research if you unwind the two
strands you can see that each has a
sugar phosphate backbone connected to
the sequence of nucleic acid base pairs
known by the letters ATG and C now the
strands run in opposite directions which
is important when you go to copy DNA
copying DNA is one of the first steps in
cell division
here the two strands of DNA are being
unwound and separated by the tiny blue
molecular machine called helicase
helicase literally spins as fast as a
jet engine the strand of DNA on the
right has its complementary strand
assembled continuously but the other
strand is more complicated because it
runs in the opposite direction so it
must be looped out with its
complementary strand assembled in
Reverse section by section at the end of
this process you have two identical DNA
molecules each one a few centimetres
long but just a couple nanometers wide
so to prevent the DNA from becoming a
tangled mess it is wrapped around
proteins called histones forming a
nucleus own these nucleosomes are
bundled together into a fiber known as
chromatin which is further looped and
coiled to form a chromosome one of the
largest molecular structures in your
body
[Applause]
you can actually see chromosomes under a
microscope in dividing cells only then
do they take on their characteristic
shape otherwise the DNA is more strewn
inside the nucleus the process of
dividing a cell takes around an hour in
mammals so this footage is from a
time-lapse you can see how the
chromosomes line up on the equator of
the cell now when everything is right
they are pulled apart into the two new
daughter cells each one containing an
identical copy of DNA now simple as this
looks the process is incredibly
complicated and requires even more
fascinating molecular machines to
accomplish it so let's look at a single
chromosome one chromosome consists of
two sausage-shaped chromatids containing
the identical copies of DNA made earlier
each chromatid is attached to
microtubule fibres which guide and help
align them in the correct position the
microtubules are connected to the
chromatid at the kinetochore here
colored red the kinetochore consists of
hundreds of different proteins working
together to achieve multiple objectives
in fact it's one of the most
sophisticated molecular mechanisms
inside your body the kinetic warp is
central to the successful separation of
the chromatids it creates a dynamic
connection between the chromosome and
the microtubules for a reason no one's
yet been able to figure out the
microtubules are constantly being built
at one end and deconstructed at the
other while the chromosome is still
getting ready the kinetochore sends out
a chemical stop signal to the rest of
the cell shown here by the red molecules
basically saying this chromosome is not
yet ready to divide
the kinetochore also mechanically senses
tension when the tension is just right
and the position and attachment are
correct all the proteins get ready shown
here by turning green at this point the
stop signal broadcasting system is not
switched off instead it is literally
carried away from the kinetochore down
the microtubules by a dining motor
that's the walking guy this is really
what it looks like it has long legs so
it can avoid obstacles and step over the
kinase ins molecular motors that walk in
the opposite direction personally I'm
astounded by these tiny molecular
machines how they're able to routinely
and faithfully execute their functions
billions of times over inside your body
at this exact instant I'm also amazed by
the scientists who were able to work out
how this happens in such detail that we
could create realistic depictions of
them like you saw in the animations in
this video but perhaps the most amazing
thing is just how much is left to be
discovered like figuring out how exactly
the chromatids are pulled to opposite
ends of the cell there is still so much
that we don't quite know you know what I
find exciting is that in science fiction
for decades we've been writing about
tiny nanobots that will be injected into
our blood streams that can heal us but
what this suggests the existence of
these tiny molecular machines inside us
it suggests that there isn't a physical
limit that would prevent that and so I
think it's pretty likely that in future
we will be able to develop our own tiny
molecular machines that will be able to
repair our bodies better than they can
repair themselves
you