Hi. It's Mr. Andersen and in
this video I'm going to show you the difference between diploid and haploid cells. And I'm
giving you a clue here in the title. Since diploid is written twice and in different
colors it tells you a little bit about what it is. But before we get to diploid and haploid
cells, let's talk about the secret of life. And the secret of life is this. That the genes
or the information on how to make a new you is going to be found in your DNA. So the DNA
contains genes. Those are simply sections of DNA that code for specific RNA. Which eventually
makes specific proteins. And those proteins eventually make you. And so we're going to
have around 20,000 genes in human DNA. Each of those are coding for a specific protein.
It's a little more complex than that. But that's what your made up of. You're made up
of proteins. And so let's look at specific chromosome. Here we're looking at chromosome
16. It's the 16th smallest chromosome that humans have. And if we dye it, if we stain
it, it looks kind of like this. It has a short and a long arm. But if we were to look way
down here, there's going to be a gene. And that gene, if there is a specific change in
it, is going to code for a specific color. And that color is going to be red in red hair.
Now there's not just one gene on chromosome 16, there's going to be around 1,000 genes
just on chromosome 16. And each of those are coding for specific proteins. But this one
right here is coding for that red hair color. Now you know however that it's not as simple
as that. You could have two parents that don't have red hair and they could have a kid that
does have red hair. And so how does that work? Well, you have two chromosomes. You are a
diploid organism. And so every cell in your body is not going to have only one chromosome
16. But you're going to have two. Now these chromosomes will look the same. When you look
at them they look very similar and that's because they are homologous chromosomes. They're
about the same length. The centromere is in the same location. They're going to have the
same genes all the way up and down. But they're going to just have different alleles or different
versions of those genes. Where did you get those two chromosomes from? You got them from
your parents. And so you got one from your dad and you got one from your mom. And so
you could have a parent who only has one of these genes for red hair. It's recessive.
And it's not going to show up in you. And so every cell in your body is diploid. What
does that mean? It has two complete sets of chromosomes and therefore two complete sets
of genes. And so what cells in our body are like that? All the cells. All the cells in
our body, at least humans, are going to be somatic cells. Somatic cell means body cell.
And so every cell is going to be diploid or 2n. N is going to refer to the number of chromosomes.
And so we have 1, 2, 3 chromosomes in a haploid cell. And if a diploid cell were going to
have two of each of those chromosomes. We're going to have a total of 6. And so where are
the haploid cells? Those are going to be the sex cells or the gametes. And so this sperm,
in humans, is going to have 23 chromosomes. The egg is going to have 23 chromosomes. Each
of those cells by themselves are haploid or n, but the somatic cells or all the cells
in our body, the body cells, are going to have 46 chromosomes. Because we get 23 from
our mom and we get 23 from our dad. And so ploidy then refers to the chromosome sets
in the nuclei. And so if we were to take a somatic cell or a body cell and take this
nucleus here and bust it apart, what would we see? We would see all these different chromosomes.
And in this image they've been dyed so you can see the different colors. We could arrange
them according to length. So the longest one is going to be chromosome 1 and it's just
going to keep going down like that. And this would be a karyotype. It's going to show that
a cell of a human is diploid. It has two copies of every chromosome. Now what does a karyotype
tell me? Not much. It does tell me that I'm a girl in this case. That we're going to have
two X chromosomes. It could tell me if I had Down Syndrome. We'd have an extra chromosome
21. But it doesn't even tell me if I have red hair. It doesn't even tell me what that
gene is. It just says that I have two copies of the 16th chromosome. And so in humans the
sex cells or the gametes are going to have half of that. And so an adult somatic cell
or body cell, we're going to say 2n=46. Well what does n refer to? It's the number of chromosomes.
And again in humans we have 23. You can see here's twenty two, here's twenty three. But
why do we put a 2 in front of the n? Because we have 2 copies of all of those. And so if
we were to look at the gametes of the sperm and the egg they're going to be n or haploid
cells. And n is only going to be 23. So 23 chromosomes in the sperm. 23 in the egg. And
when we fertilize that egg we're back to a diploid cell again. And so you should know
this. That in humans we spend most of our life being diploid or 2n. But it's not the
same in all organisms. All organisms are going to move through, or eukaryotic organisms are
going to move through this diploid phase and then a haploid phase. And so you might think
well how do we move from haploid to diploid? Remember, when two gametes come together that
forms a zygote. And that process is called fertilization. So when sperm fertilize egg
that fertilization process is going to move up into the diploid region. And likewise when
we go from 2n to n, that's meiosis. When we're creating new cells that are haploid or have
half the genetic information. And it's also mixed up or there's variable in that. And
so let's look at this human right here. So the human, adult human, is going to be diploid
in nature. Every cell in it's body, except for its sex cells, are going to be diploid
or two copies of all the chromosomes. How do we eventually get back to another human?
Well we're going to have meiosis where in the male, we produce sperm, and the female,
we produce egg, but we're quickly going to have fertilization and then we're back into
the diploid realm. We're going to have a zygote that eventually gets bigger and forms a new
organism. And so when you're looking at me, you're looking at cells that are diploid.
What's the advantage of that? Well one thing is we kind of have a back up copy for all
our genes. If something goes wrong we have another one. We also can have variability
in that. We can have genes like sickle cell anemia that can hang out and eventually they
come in handy later. But it's not the only way life is built. So if we were to look at
algae, these algae here which are microscopic plants, most of them are going to be haploid.
And so each of these only has one set of chromosomes. Or one set of genes in it. What's the advantage
of that? It's easier. It doesn't take as long to copy all of that DNA. But they still go
through the life cycle. They're still going to have fertilization. Quick meiosis back
to cells that are haploid again. And so they're just going to be haploid. Or mushrooms. The
number of different fungi are going to be haploid. Each cell is going to have one complete
set of genes or one set of chromosomes. But they still will go through fertilization,
meiosis, back to cells that form a mushroom. If we were to look at some of the higher plants,
like this evergreen tree here, it's going to be diploid. All the cells in it are going
to have 2n, or it's going to have two copies of every gene. But it will still go through
meiosis, fertilization and then we're back to 2n. But very simple things like a moss
or a liverwort are going to spend a lot of their time down here in the haploid. And so
again there's variety in life. And it's played against you know the advantages in their specific
environment. And there are going to be somethings where we get, you know, triploid or tetraploid
or polyploid. In fact plants are made by having mistakes where we increase the number of chromosomes
and it can create a new plant. I think there's a type of plant called the Adder's Tongue
has 1024 ploid. It has so many chromosomes. It has so many genes but it still works. I'll
leave you with a really tough question. The tough question is this. Bacteria, what's their
ploidy? In other words are they haploid? Are they diploid? Now they're not going to go
through meiosis remember. They're going to go through binary fission. But what are they?
Well the right answer is that they're somewhere between haploid and diploid. So what's their
ploidy? It would be like 1.2 or 1.8. Well how does that work? If you have a bacteria
the DNA gets copied really really quickly. And so they're quickly going to copy their
DNA but it takes much longer to make the proteins that eventually build two bacteria. And so
if we were to look at all of these bacteria, some of them are going to have, you know,
one. But some of them are going to have 1.2, 1.8. They're going to be somewhere between
the two. And so what is ploidy? It's going to tell us the number of chromosome sets that
we have. Again it's different in all forms of nature, and I hope that was helpful.
