Name: DNAの構造と複製。クラッシュコース生物学 #10 (DNA Structure and Replication: Crash Course Biology #10)
Uploaded: 2021-01-14T04:20:40.000Z
Duration: 12 min 59 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

It's just beautiful, isn't it? It's just mesmerizing. It's double hel-exciting!

You really can tell, just by looking at it, how important and amazing it is.

関係詞節（制限と非制限）

It's pretty much the most complicated molecule that exists, and potentially the most important one.

It's so complex that we didn't even know for sure what it looked like

So multifariously awesome that if you took all of it from just one of our cells and untangled it,

Now consider that there are probably 50 trillion cells in my body right now.

Laid end to end, the DNA in those cells would stretch to the sun.

Of course you know I'm talking about deoxyribonucleic acid, known to its friends as DNA.

DNA is what stores our genetic instructions -- the information that programs all of our

It's a 6-billion letter code that provides the assembly instructions for everything that

And it does the same thing for pretty much every other living thing.

I'm going to go out on a limb and assume you're human.

In which case every body cell, or somatic cell, in you right now, has 46

chromosomes each containing one big DNA molecule.

These chromosomes are packed together tightly with proteins in the nucleus of the cell.

And so is its cousin, which we'll also be talking about, ribonucleic acid, or RNA.

Now if you can make your mind do this, remember all the way back to episode 3, where we talked

about all the important biological molecules:

carbohydrates, lipids and proteins. That ring a bell?

Well nucleic acids are the fourth major group of biological molecules, and for my money

they have the most complicated job of all.

Structurally they're polymers, which means that each one is made up

of many small, repeating molecular units.

In DNA, these small units are called nucleotides. Link them together and you have yourself a

Now before we actually put these tiny parts together to build a

DNA molecule like some microscopic piece of Ikea furniture, let's

first take a look at what makes up each nucleotide.

DNA gets the first part its name from our first ingredient, the sugar

But all the really significant stuff, the genetic coding that makes you YOU,

is found among the four nitrogenous bases:

adenine (A), thymine (T), cytosine (C) and guanine (G).

It's important to note that in living organisms, DNA doesn't exist

as a single polynucleotide molecule, but rather a pair of molecules that

They're like an intertwined, microscopic, double spiral staircase.

Basically, just a ladder, but twisted. The famous Double Helix.

And like any good structure, we have to have a main support.

In DNA, the sugars and phosphates bond together to form twin backbones.

These sugar-phosphate bonds run down each side of the helix but, chemically, in opposite directions.

In other words, if you look at each of the sugar-phosphate backbones, you'll see that

one appears upside-down in relation to the other.

One strand begins at the top with the first phosphate connected to the sugar molecule's

5th carbon and then ending where the next phosphate would go, with a free end at the

This creates a pattern called 5' (5 prime) and 3' (3 prime).

I've always thought of the deoxyribose with an arrow, with the oxygen as the point.

Now on the other strand, it's exactly the opposite.

It begins up top with a free end at the sugar's 3rd carbon and the phosphates connect to the

And it ends at the bottom with a phosphate.

And you've probably figured this out already, but this is called the 3' to 5' direction.

Now it is time to make ourselves one of these famous double helices.

These two long chains are linked by the nitrogenous bases via relatively weak hydrogen bonds.

But they can't be just any pair of nitrogenous bases.

Thankfully, when it comes to figuring out what part goes where, all you have to do is

remember is that if one nucleotide has an adenine base (A),

only thymine (T) can be its counterpart (A-T).

Likewise, guanine (G) can only bond with cytosine [C] (G-C).

These bonded nitrogenous bases are called base pairs.

The G-C pairing has three hydrogen bonds, making it slightly stronger than the A-T base-pair,

It's the order of these four nucleobases or the Base Sequence that allows your DNA

So, AGGTCCATG means something completely different as a base sequence than, say, TTCAGTCG.

Human chromosome 1, the largest of all our chromosomes, contains a single molecule of

If you printed all of the letters of chromosome 1 into a book, it would be about 200,000 pages

And each of your somatic cells has 46 DNA molecules tightly packed into its nucleus

-- that's one for each of your chromosomes.

Put all 46 molecules together and we're talking about roughly 6 billion base pairs

If we were to fill it with our DNA sequence, we'd need about 10,000 of them to fit our

Let's test your skills using a very short strand of DNA.

I'll give you one base sequence -- you give me the base sequence that appears on

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DNAの構造と複製。クラッシュコース生物学 #10 (DNA Structure and Replication: Crash Course Biology #10)

sugar

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