- [Instructor] Hi, everyone.
This video is all about how the information
in an organism's genes is expressed as its traits.
This occurs through the action of molecules called proteins.
But before we get into the details,
let's start with the basics.
What are traits?
Well, traits are an organism's observable characteristics,
and there are some really weird
but really cool traits out there in the animal kingdom.
Spiders, for example,
can make seven different types of silk.
Elephants have an amazingly low risk of developing cancer.
And some jellyfish have the ability to glow.
That's right!
The crystal jelly can bioluminesce,
or glow in the dark, all on its own.
So now let's dive into the details
of how these traits are expressed.
Specifically, let's look at
the jellyfish trait of bioluminescence.
We know that an organism's traits are affected by its genes.
So let's travel into the nucleus
of the crystal jelly's cells to where its genes are found,
on chromosomes.
A chromosome shown here is a cell structure
that contains a coiled up DNA molecule.
I personally like to think of chromosomes
as the packaged and organized version of DNA.
A DNA molecule is made up of subunits, called nucleotides.
Nucleotides are often called A, T, C, and G,
which stand for adenine, thymine, cytosine, and guanine.
A gene is a specific stretch
or a chunk of nucleotides within a DNA molecule.
So a chromosome and its DNA are like a cookbook
that contains recipes for making an organism.
Genes are the recipes.
And just like how letters are arranged in a specific order
to form words in a recipe,
the nucleotides in a gene
are also arranged in a specific order to convey information.
So what does the cell make with these gene recipes?
The cell uses the information in genes
to make other molecules called proteins.
So our crystal jelly must have genes on its chromosomes
that are responsible for its trait of bioluminescence.
Because of work done by scientists,
we now know that the jelly fish's bioluminescence
involves one gene in particular.
The coding sequence of this gene
is made up of roughly 700 nucleotides,
all arranged in a specific order.
And this gene acts like a recipe for making a protein
called green fluorescent protein, or GFP, for short.
Whenever you hear the word fluorescent,
just think glowy.
GFP is a glowy protein that can emit green light.
And it's this presence of GFP in the jelly fish's cells
that allows the jellyfish to bioluminesce.
But proteins can do so much more than glow.
There are thousands of tasks
that different proteins carry out
in order for cells to function.
Some proteins help provide structure,
some help move substances into and out of the cell,
and others help carry out chemical reactions.
All proteins are made up of subunits called amino acids
which are connected in a chain.
It's the order of nucleotides in a gene
that determines the order of amino acids in a protein.
And the order of amino acids is important
because it determines the 3D shape
that the protein will take on.
And a protein's shape, in turn, affects its function.
For the GFP protein,
this protein has a special sequence of three amino acids
that end up in the middle of a barrel-like structure
when the protein takes on its 3D shape.
These amino acids form the part of the protein
that can fluoresce.
They can absorb energy
and then emit that energy as green light.
So to sum it all up, genes affect traits
through the actions of the proteins that they encode.
The order of nucleotides in a gene
determines the order of amino acids in a protein.
And a protein's amino acids determines its structure
and its function.
The crystal jelly's bioluminescence
and the discovery of GFP
highlight why this knowledge is so important.
Scientists have used the GFP gene and protein
to make countless discoveries.
Now, researchers can attach GFP to other things,
such as other proteins or viruses,
making them visible through bioluminescence
and easy to track.
GFP has made the invisible visible,
and it's allowed researchers to learn how neurons develop
and how cancer cells spread.
And all of this research started
with wondering about a single trait
observed in the crystal jelly.
Similarly, scientists are studying the properties
of spider silk proteins
in order to make new biocompatible materials.
And they're also studying elephants
for clues about how to prevent cancer in humans.
What animal trait do you think will lead
to the next big discovery?