Human DNA consists of 23 pairs of chromosomes with over 3 billion nitrogenous base pairs.
Surely we don’t need all that to function right, I mean, how hard can it be?
Hey there peoples, Julian here for DNews.
I’m sure what I’m about to say is review for many of you but just to make sure everyone’s
on the same page I’ll reiterate: you need DNA.
Red blood cells being the exception, all the cells in your body have it.
For most of those cells you have 23 pairs of long DNA sequences called chromosomes.
The DNA is structured like a spirally ladder and the rungs of these ladders are the nitrogenous
base pairs Adenine and Thymine, and Guanine and Cytosine.
You repeat and rearrange those 4 bases enough and bingo, you got yourself the blueprint
to build a human being.
Or a potato.
How you arrange them is key.
Ok, everybody up to speed?
Great.
So just how many base pairs do you need?
For a human, not a potato.
When we examine our 23 chromosomes it would seem the answer is a little more than 3 billion.
Three billion ATGCs to make a Steve.
A potato only has only 840 million base pairs by comparison, and that makes sense right?
Steve is a pretty complex guy, certainly more so than a potato.
Though interestingly the potato has 24 pairs of chromosomes to our 23, they’re all just
a lot shorter.
But don’t be mislead into thinking that more DNA = more awesomeness.
An organism with a genome 50 times bigger than ours isn’t going to necessarily be
a telepath or have laser vision or the power to control magnetic fields or an increased
healing factor.
It could be something as simple as a flower.
Actually it is.
At over 150 billion base pairs in length, the flower Paris japonica is the largest genome
ever accurately measured.
The ameboid Polychaos dubium was estimated to be even bigger, at 670 billion base pairs,
but it’s claim to the throne is disputed because the techniques used to measure genome
size in the 60s have since proven flawed.
It’s not the size of the DNA, it’s how you use it.
At the other end of the spectrum there are bacteria with genomes that don’t even break
a million base pairs.
Nasuia deltocephalinicola has the smallest genome ever discovered, measuring in at just
112 thousand base pairs, though it needs to live in symbiosis with another bacterium to
survive.
Nanoarchaeum equitans gets by with a scant 490 thousand base pairs encoding 540 genes,
it’s the smallest independent cellular unit discovered yet.
Scientists recently synthesized a minimalist genome of just 530 thousand base pairs that
encode just 473 genes by whittling away 70 thousand base pairs of the already diminutive
Mycoplasma genitalium.
That’s right, organisms can live without all their DNA.
In fact it’s estimated that you’re only using about 8% of your genome. 1% of it is
coding proteins, 7% is regulating when to use that first 1%, and the remaining 92% is
just junk as far as we can tell.
That number is disputed, and by a different measurement and the loosest definitions as
much as 80% of our DNA may serve some function, but that still means 60 million base pairs
are just along for the ride.
Evolution provides a good explanation for why we’re carrying around all this extra
baggage: becoming human was a long and messy path.
Along the way some DNA is going to mutate into disuse but keeping it around won’t
be too much of a hassle.
In fact having all that extra ATGC to work with means mutations are less likely to occur
on an essential gene and therefore won’t be catastrophic.
It may actually be beneficial, giving random chance the opportunity to mutate junk DNA*
into something useful and giving an organism an edge.
As a bonus the process of evolution explains why a flower can have 50 times more DNA than
we do.
Just how much of your DNA is junk is still up for debate.
It may actually be used to make important things, like your face.
Anthony Carboni explains here.
Are you surprised about your genome being bloated or is it no big deal to you?