Hi. It's Mr. Andersen and welcome to biology video essentials 52. This is on
cellular variation. If I could summarize this whole podcast in one quote it would be this,
that "Variety is the spice of life". So the greater the variation the more likely a cell
is able to deal with changes in their local environment. And so example of this. In plants
the one magical chemical that can take energy from the sun and convert it into usable energy
is chlorophyll. Chlorophyll A. This is the spectrum of chlorophyll A. So it obviously
loves color in the red. It loves color in the purple and blue. But it doesn't deal so
much with colors in the green. And that's why plants are green. They're reflecting that
light. They don't make usable energy from it. But plants also over time evolved a different
type of chlorophyll called chlorophyll B. Chlorophyll B is able to pass off some of
that energy to chlorophyll A during photosynthesis. But what it allows them to do is it allows
them to absorb more of the spectrum of light. So it allows them to use more of the energy
of the sun. So just by getting a little variability in the chemical structure of chlorophyll,
they're able to do better as an organism. Variety again is the spice of life. And so
basically I'm going to talk about how variation in the molecules of cells can increase their
success. Example I'll talk about is phospholipids. And a great example of that is winter wheat.
How they can vary the amount of phospholipids. And then I'll talk about genes. And so how
variation in the actual genes can give them heterozygous advantage. An example we've talked
about before is sickle cell disease. And then finally I'm going to talk about something
that's relatively new. And that's gene duplication and the importance of that in organisms. Example
I'll talk about is the antifreeze gene that's found in a number of different organisms that
live in really cold environments. And so let's start with molecular variation. So this is
going to be variation within the molecules of a cell. So since you've made it all the
way to podcast 52 you've seen the podcast on phospholipids. Phospholipids essentially
have two parts. They have a hydrophilic head. And then they're going to have a hydrophobic
tail. And so these make up all the membranes in all of the cells essentially. And so basically
this would be the phospholipids. And again they float horizontally back and forth. They're
flexible. And so they allow material to move back and forth. But depending on how those
fatty acid tails are, they have a different behavior. And so basically if you get a double
bond here, because you lack hydrogen, there will be a kink on this tail. And those kinky
tail will cause the phospholipids to move farther apart. So they can't get quite as
close together. And so as the temperature gets colder and colder and colder, these phospholipids
are going to get closer and closer together. And so a way to deal with changes in temperature
is to have more of these unsaturated fatty acids in the tails. And so they can't pack
as closely together. And so winter wheat is a type of wheat that we grow here in Montana.
I think it came from Russia originally. But basically what happens is you plant it in
the fall. It'll start to grow. And then all of a sudden snow will come. Snow will come.
And now when spring comes it can start growing again. It kind of has a head start on spring
wheat, which you're going to plant in the spring. And so what scientists have found
is that there's an increase in the amount of unsaturated fats and they can vary the
amount of unsaturated fats in the wheat. In other words you could grow wheat in a warm
temperature and in a cold temperature. And you're going to find that they're able to
produce more of the unsaturated fats during a period of time when it's cold. And so what
that means is cells are able to create more molecules or a variety of molecules depending
on their local environment. And I think there's something like eighteen different types of
phospholipids that are created in cells. And so I had this idea at one time when I was
learning biology that phospholipids were boring. And it's the proteins that are important.
But we're finding that the phospholipids are just as important as the proteins as well.
Okay. Next we're looking at the genes. And so heterozygote advantage, heterozygote advantage
is when you have two copies of a gene and that gives you some kind of an advantage.
And so this is the most deadly animal we have on our planet. It's the anopheles mosquito.
It passes an organism called the plasmodium. Basically what it does is causes malaria.
Malaria is killing more people every year than any other disease on our planet. And
so basically there's a huge amount of selective pressure. Especially in sub Saharan Africa.
And so the story of heterozygote advantage is that if you have a sickle cell disease
or you have a sickle cell gene, you produce red blood cells that have this sickled appearance.
Basically it's a mutation or a change in a single letter in the gene that makes the protein
hemoglobin in our blood. And so if you have two copies of that you make sickle cell blood.
And so if we look at this study here. This is a study that was done in Kenya on children
that were born. So this is 100% of the children that were born here. And then they looked
at how many of them survived, days after they were born. And so to kind of get this set,
this would be 77% of them living you know something like 4-5 years later in this study.
And so basically what they found is that if you have sickle cell disease, a number of
those children are going to die off. And that's just due to complications in the sickle cell
disease. But if you have perfectly good blood, then this is going to be the survivorship
curve. But if your heterozygote, in other words, you have one copy of the sickle cell
gene, but you have one good copy. We see a survivorship curve that's actually greater
than that with no problem. In other words the heterozygotes are doing better. And the
reason why is that by having that one gene, you make your red blood cells a little different.
And so it can't be infected by this plasmodium. So it can't be effected by the malarial disease.
So you're given protection against that disease. And so again in this case, why do we have
sickle cell disease show up in much higher percentage in those whose ancestors come from
Africa? It's because it gave them protection against malaria. In other words genes and
having a variety of genes can actually help. The last one I want to talk about is gene
duplication. And I want to start with an analogy. Most of you've never seen this movie, but
it's called Multiplicity. Hopefully I'm spelling that right. And it was a Michael Keaton movie.
It's a comedy. Basically he discovers how he can make a clone of himself. And so he
clones himself. And so essentially if I were to do this I would make a clone of myself
who could go to school and teach. I make a clone of myself who could make podcasts. I
make a clone of myself who can clean my house. So his idea is that he can now do the things
that he wants to do in life. And he doesn't have to do all these other tasks. Now of course,
it's a comedy. So the clones get dumber and dumber over time. And they make clones of
themselves. And so it kind of spirals out of control. What's this analogy you've been
telling us. Well, genes do the same thing. They have the same idea that Michael Keaton
does. And so basically what they do, scientists had thought about this for a long period of
time, is if a gene duplicates itself. So it makes a copy of itself. Then this gene, right
here, can continue doing its job that it always does. But the clone of that gene, since it
doesn't have to do this job of the original gene, can do something else. So it can take
on another task. In other words, once it's duplicated itself, and this is a little deep,
now it doesn't have to adhere to natural selection. It's outside of that selective process. And
so it can become anything it wants to. And so scientists had theorized for a long period
of time that this is a way that we can actually get evolution or evolutionary novelty. And
so we're starting to see how this actually works. This is a fish right here called the
eelpout. This a is picture taken from a submersible. And you can see an eelpout right here. And
so basically they're able to live in temperature that is near or below freezing. And that's
due to pressure. You could actually go below 0 degrees Celsius. And so they wondered how
this could be. And they discovered that there's an antifreeze protein. This is a subclass
3 antifreeze protein that's found in these eelpouts. Basically ice crystals aren't going
to start to form in their cells because of this protein that they have. And so how could
this evolve? Well what they theorized for a long period of time is that it may be through
gene duplication. Maybe we had a gene that did something before, but once it had been
duplicated, or once it had been cloned, it could become something else. And so when they
looked at it they found that it looked a lot like this enzyme that's used in digestion.
Sialic acid synthase. It's actually found in humans. And so this scientist right here,
her name is Christina Cheng, just within the last few years has identified both of these
genes. And she's able to show just by sequencing of the genes that this is how it formed. It
formed through this gene duplication or this cloning of the gene. And that's how almost
all of these antifreeze proteins came to be. In other words they were enzymes that did
one thing. Once these were freed from doing that job, they were able to evolve into another
process. In this case becoming an antifreeze protein. And so again that's how we can get
variation within cells. And again variation leads to variety which leads to the spice
of life. And I hope that's helpful.