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.