(OLD VIDEO) DNA Replication: The Cell’s Extreme Team Sport

(OLD VIDEO) DNA Replication: The Cell’s Extreme Team Sport

Captioning is on. Click the CC button at bottom right to turn off. Follow us on Twitter (@amoebasisters) and Facebook! DNA. We talk about it so much—it is the
ultimate director for cells and it codes for your traits. It’s a major component of what
makes you, you. When you have a really important molecule like DNA that is ultimately responsible
for controlling the cell…it would make sense that when you make another cell (like in mitosis),
you would also have to get more DNA into that cell. And that introduces our topic of DNA
replication, which means, making more DNA. First let’s talk about where and when.First
where—it occurs in the nucleus. If the cell has a nucleus. Remember, not all cells have
a nucleus. This video clip is actually going to focus on the types of cells that do have
a nucleus though known as eukaryote cells. Prokaryotes, which are cells that lack a nucleus,
do things a little differently. Next When does this happen—this typically happens
during a stage known as interphase. Interphase is when a cell’s growing, it’s carrying
out cell processes, and it’s replicating its DNA. You know what it’s not doing at
the exact same time? Dividing. You don’t want a cell to be replicating DNA and dividing
at the exact same time. That’s a little bit too much multitasking. So DNA replication
does not happen during cell division (aka mitosis). In fact, the cell replicates its
DNA before division processes like mitosis and meiosis. Because once you make that new
cell, you better have DNA to put in there. I think DNA replication would actually make
a great video game. It’s actually quite exciting. I’m going to introduce the key
players in DNA replication so that you can get some background information. The majority
of these key players that I’m going to introduce are enzymes. In biology, when you see something
end in –ase, you might want to check as it is very possible that it’s an enzyme.
Enzymes have the ability to speed up reactions and build up or break down the items that
they act on. So here we go with the key players. Helicase- the unzipping enzyme. If you recall
that DNA has 2 strands, you can think of helicase unzipping the two strands of DNA. Helicase
doesn’t have a hard time doing that. The hydrogen bonds that hold the DNA strands together
is pretty weak compared to other kinds of bonds. DNA Polymerase- the builder. This enzyme
replicates DNA molecules to actually build a new strand of DNA. Primase- The initializer.
With as great as DNA polymerase is, poor DNA polymerase can’t figure out where to get
started without something called a primer. Primase makes the primer so that DNA polymerase
can figure out where to go to start to work. You know what’s kind of interesting about
the primer it makes? It’s actually a piece of RNA. Ligase- the gluer. It helps glue DNA
fragments together. More about why you would need that later. Don’t feel overwhelmed.
We’ll go over the sequence in order. Please keep in mind, that like all of our videos,
we tend to give the big picture but there are always more details to every biological
process. There is more involved than what we cover. DNA replication starts at a certain
part called the origin. Usually this part is identified by certain DNA sequences. There
can be multiple origins within the DNA strand. At the origin, helicase (the unzipping enzyme)
comes in and unwinds the DNA. SSB proteins (which stands for single stranded binding
proteins) bind to the DNA strands to keep them separated. Primase comes in and makes
RNA primers on both strands. This is really important because otherwise DNA polymerase
won’t know where to start. Now comes DNA Polymerase. Remember, it’s the important enzyme that adds DNA bases. Now you have 2 strands right? But they’re not identical.Remember they complement each other. They also are anti-parallel so they don’t really
go in the same direction. With DNA, we don’t say it goes North or South. The directions for the DNA strands are a little different. We say that DNA either goes 5’ to 3’ or
3’ to 5’. What in the world does that mean? Well the sugar of DNA is part of the
backbone of DNA. It has carbons. The carbons on the sugar are numbered right after the
oxygen in a clockwise direction. 1’, 2’ 3’, 4’ and 5.’ The 5’ carbon is actually
outside of this ring structure. Now you do the same thing for the other side but keep
in mind this strand is flipped just because DNA strands are anti-parallel to each other.
So let’s count these—again, clockwise after the oxygen. 1’, 2’ 3’, 4’ 5’.
And the 5’ is out of this ring. This strand on the left runs 5’ to 3’ and the strand
on the right here runs 3’ to 5’. Well, it turns out that DNA polymerase can only
works in the 5’ to 3’ direction. So…the strand that runs 5’ to 3’ is fine. It
is called the leading strand. But the other strand will make it a little tricky. DNA polymerase
can only go in the 5’ to 3’ direction. (NOTE: Reads in 3′ to 5′ direction). Primase has to set a lot of extra primers down to do that as shown here. It takes longer too.
This strand is called the lagging strand which is pretty fitting.On the lagging strand, you
tend to get little fragments of synthesized DNA. These are called Okazaki fragments. Okazaki.
What an amazing name. The primers have to get replaced with DNA bases since the primers
were made of RNA. Ligase, the gluing enzyme as I like to nickname it, has to take care
of the gaps in the Okazaki fragments.Now at the end, you have two identical double helix
DNA molecules from your one original double helix DNA molecule. We call it semi-conservative
because the two copies each contain one old original strand and one newly made one. One
last thing. Surely you have had to proofread your work before to catch errors? Well, you
definitely don’t want DNA polymerase to make errors. If it matches the wrong DNA bases,
then you could have an incorrectly coded gene…which could ultimately end up in an incorrect protein—or
no protein. DNA polymerase is just awesome…it has proofreading ability. Meaning, it so rarely
makes a mistake. Which is very good. That’s it for the amoeba sisters and we remind you
to stay curious! Follow us on Twitter (@amoebasisters) and Facebook!

100 Replies to “(OLD VIDEO) DNA Replication: The Cell’s Extreme Team Sport”

  1. June 2019 UPDATE: This older video has been updated here: https://youtu.be/Qqe4thU-os8 ! The new video has a very similar script but improved drawings and a bit more detail than before! Don't worry, we have NO plans to delete this old video.
    We know there is sometimes confusion about DNA polymerase; we see it in comments and also on online discussions. We wanted to make a clarification to pin here that might be helpful! We mention DNA polymerase works in the 5' to 3' direction on the new strand as it adds nucleotides to the 3' end. (see 6:09). This is the direction that the new strand grows. But it's important to understand we are referring to the new strand drawn in (not the old, template strand) and we don't use the word move when referring to the DNA polymerase. For example, let's say you were considering, "What direction does DNA polymerase move on the old (template) strand?" In that case, if you notice from our video illustration, the DNA polymerase is moving 3' to 5' on the old (template) strand. It matters (1) what you are specifically asking about DNA polymerase and (2) whether you are referring to the old template strand or new strand being made. Overall, it is important to understand that DNA polymerase is working to elongate the new strand in the 5' to 3' direction, and this is why there is a leading and lagging strand. We love DNA replication- we hope to someday update this video with improved graphics and more clarifications within the video.

  2. You girls have been around for a while now and i like your videos but sis…. you need a better mic:) and thats just FAX

  3. My life is slowly coming to an end.

    Edit: Like this comment for it to be on top of the list so this is the first thing people read when watching this vide in class. 😉

  4. This is so great! Their video are always very understandable and logically organized and clears misconceptions. I’ve always like their vid so much.

  5. Amazing video! Wayyy better than my teacher's powerpoints and lessons. This video helped me understand the topic; thank you!

  6. Such an excellent video. I laughed a bunch of times!! keep up the good work, you have an excellent talent. definitely subscribing, can't wait for more content (:


  8. Wow….its a wonderful, simple , beautifull and friendly explanation i ever known… which you made even more easier with simple and funny diagrams…thanq so much for your effort…🤗

  9. Thank you so much! This video was so incredibly helpful. I understand everything now, and I even got an A on my quiz on DNA replication today! You guys are awesome. ✨

  10. Helpful but really hard to look at. The video is good but the visual animation is really ugly. I’m glad now there animation isn’t a eye sore.

  11. ————————–$$$$$$

  12. I’m from England so my exam specification is entirely different , but these videos are so helpful I have not came across such clear and concise biology videos in years

  13. this is soooooooo much better than reading my professors note on this subject. I actually understand the concept now. thanks

  14. I would like to share something I know about DNA Replication, the base enzymes are two pairs, but there are four pairs altogether working in unison. This is called the Quadripple Helix Center. It is located at the center of a DNA Helix. DNA and RNA are like partners in replicating biological tissues. This is called DNA and RNA Replication. It is in fact a blue print for replicating biological tissues. Some people called it organs cloning. But I like to called it DNA and RNA Replication. By extrapulating a few strands off of the DNA Helix of a human genome or an animal genomes or a fish genomes, we can replicates any organs we want. I hope this help.

  15. And if im correct the DNA starts and ends with Adenine. Its like adenine leaving one side of the heart to travel through the pulmonary artery to the lungs to pick up the O-molecules u inhale and release the carbon Dioxide and then travel back to the heart as Guanine (O-Rich) so that the Oxidation and Polymerization can occur correctly and keep from the acidity, salinity, and PH level from going haywire.

  16. This helped me so much, I was completely and utterly clueless and I just couldn't visualise it in my head when I was trying to previously study it. However, now it makes so much more sense. Thank you 💚

  17. Thank you so much! Me and the missus tackled some genetics this week for an upcoming exam, and it's left us just scratching our heads (we literally just got prints to study off of on our own, and the technical lingo is pretty bewildering), so breaking it down like this has been a tremendous help!

  18. The only thing I wondered throughout the video was that how on earth did scientists discover this crazily tiny stuff !!!

  19. On this other video I found it shows the lagging strand being drawn out in loops, rather than in just a straight line like the leading strand. How can they both be correct?


  20. I absolutely love this channel, I watch it for my 10th Grade Biology class, before I watch all the other videos my teacher assigns. And literally every time I watch one of these videos, the concept actually makes sense, which is awesome cause, I do extremely well, in History, English and French, classes, but barely pass my Math and Science classes because numbers and equations and all this complex stuff makes no sense, so thank you

  21. DNA polymerase makes a mistake approximately 1 out of every billion base pairs copied. DNA polymerase is able to detect its own errors and when it does, it backs up and calls upon an enzyme called "exonuclease" to remove the wrong nucleoside and then the DNA polymerase moves forward again to continue copying the DNA strand.

  22. you guys are awesome . you explain so much thing in such a easy way in a very short time . love it . thank you

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