Life.
What is it?
As a geneticist, I would point you towards
this molecule, DNA.
Watson and Crick called it the secret of life, and that's
because this molecule has the ability to
make copies of itself.
And these copies get passed from generation to generation.
And this has been happening since the origins of life.
Every living thing has DNA.
The extraordinary diversity of life that we see around us
comes from the fact that different organisms have
slightly different versions of the DNA molecule.
In the case of humans, our DNA codes for about 22,000 genes,
and these genes are organised onto chromosomes.
The human genome contains 23 pairs of chromosomes plus the
mitochondrial DNA.
And throughout this series, we'll be featuring a new video
every day looking at each of these one by one.
[BIRD CHIRPING]
So if we imagine for a moment that these are some human
chromosomes, then Chromosome One is the biggest one.
Human Chromosome One contains about 2,000 genes, and these
are arranged along the chromosome.
So you're going to have some bits that are packed with
loads of genes and might have some big gaps in between.
But these are all along the chromosome.
And these genes do different jobs.
For example, one of the genes on Chromosome One is a gene
for the amylase enzyme, which digests starch.
And amylase is in your saliva.
And different genes along the chromosome have different jobs
to do and different times and places when they should be
doing them.
So you have genes involved in digestion, you've got genes
involved in growth and heart muscles and all of these
different functions in your body.
And one thing that the chromosome structure does is
it doesn't lie there in a straight line.
It's actually looped around like spaghetti.
And you have some genes that are hidden in this structure,
and they are not active, and other ones that are turned on.
And so the chromosome structure helps the right
genes be turned on in the right time and place.
But there's something else as well that the chromosome
structure helps, and that is that all important process of
cell division when the DNA needs to be copied and sent to
the next generation.
With 22,000 genes, that's a bit of a mess.
But instead if the genes are on chromosomes, the job gets a
lot simpler.
So if we're partitioning out these chromosomes between
daughter cells, we keep one Chromosome One there, send the
other one to a new cell, keep one Chromosome Two, send the
other to a new cell, and the same thing for the other
chromosomes.
So instead of having this big messy job to do, we've got a
comparatively simple job to do.
So this accurate and faithful copying of DNA has carried
this genetic information from generation to generation right
through all living organisms.
And you could say that this is the secret of life.