DNA Replication | Genetics | Biology | FuseSchool

DNA Replication | Genetics | Biology | FuseSchool

It might be hard to believe, but at the very start of your life you were a single, microscopic cell called a zygote. Your body now contains millions of cells, which all came about by the process of cell division.

Cell division happens when one cell divides to form two cells and it is the basis of growth and repair in humans. It is also used for asexual reproduction in organisms like bacteria.

But, a single cell cannot just split itself in half to form two whole new cells - they would essentially only be half a cell. Before the cell divides everything inside needs to be copied - this includes all the parts of the cell like the mitochondria, as well as the chromosomes inside the nucleus.

A human body cell contains 23 pairs of chromosomes - 46 altogether. During cell division, the DNA in the chromosomes is copied, or replicated to form 46 pairs (92), double the number of chromosomes. These pairs split apart when the cell divides to form two new daughter cells, each having the correct number of chromosomes. The splitting apart of the chromosome pairs happens during a stage in cell division called mitosis. [insert link to ‘mitosis’ video]

Let’s take a closer look at DNA replication.

DNA is made up of many nucleotides, each containing a base represented by the letters A, T, C and G.
A piece of DNA contains two strands of nucleotides, twisted together to form a double helix. The strands are complementary, this means that whenever there is an A in one strand, it will be joined to a T in the opposite strand and whenever there is a C it will be joined to a G.
If you are not familiar with the structure of DNA then take a look at the video What is DNA?

During DNA replication, the double helix unwinds. Then, an enzyme called DNA helicase unzips the DNA so the two strands are separated. This happens at several points along the DNA.

An enzyme called DNA polymerase attaches itself to the DNA strands and is used to add complementary free nucleotides to the now exposed bases on both strands. A pairs with T, and C pairs with G. This forms two DNA molecules, each of which have one brand new strand, and one from the original DNA.

These two strands twist to form a double helix. The two new DNA molecules are both identical to the original DNA molecule.

In some ways, DNA replication is similar to transcription, a process that happens during protein synthesis.They both use enzymes to join free nucleotides together and they both take place in the nucleus. But there are important differences: In DNA replication, each DNA strand is used as a template to make two new identical DNA molecules. In transcription, the coding strand of the DNA molecule is used to produce a single strand of RNA.

So, to recap. In this video you have learnt why DNA needs to be replicated before a cell divides and how this takes place.

CREDITS
Animation & Design: Bing Rijper
Narration: Dale Bennett
Script: Gemma Young

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[heidibordeleau]

The animation of DNA replication is good! It is simplified but right on level for high school biology. However, the information given about chromosomes is just plain wrong. Please fix this! Chromosomes before replication are "I" shaped. Only after they have been replicated (after synthesis phase) are they "X" shaped. There are never 92 chromosomes in a healthy human cell. During replication the cell goes from 46 "I" shaped chromosomes to 46 "X" shaped chromosomes. This reinforces a major misconception that many students have. Again, please fix this!

[MrCringedragon]

One tiny problem I noticed was that you used Thymine in the graphic describing RNA, when it should be Uracil (2:55)

[cynthiachan]

I really love the graphics of this video, I love the unzipping action and how complementary base pairs are added, but I cannot show this to my students because of the many incorrect illustrations as pointed out by other people here:
(1) incorrect way chromosomes are duplicated
(2) RNA strand should have U instead of T
(3) the 2 strands of DNA are replicated in opposite directions
I absolutely love this video otherwise but these errors are too big to ignore. I can see that people have pointed out the errors from a year ago and they have not be corrected yet. If these errors are fixed, this video would have been perfect.

[leannekirby]

I appreciate the simplicity of this video. It is just the right level of detail for my class. The details spoken of by other commenters can come at a higher level of schooling.

[akashalihazarika]

You have wrongly displayed the process. DNA replication is semi discontinuous, you have protraited it as a continuous process.

[monirasultana]

Oh you've missed the description of leading and lagging strands in dna replication, they are much more important in replication because the way differs from one strand to another strand, the lagging and the leading one, ,hope future videos will be on explaining the scrutinized things of replication, including terms like these, 😊😊😊😊

[louiseauty]

I'm disappointed, Fuse school videos are usually really good but the error with the chromosomes means I can't share it with students. Please can you fix it? A chromosome looks more like an I and then when it replicates it forms 2 chromatids joined at the centromere and looks like an X. Then the two sides pull apart to make two I shaped chromosomes, one in each cell. Your error is a really common misconception that students need to fix and your video just feeds that misconception.

[Science-Made-Easy]

Straight to the point, simple video !
I enjoyed watching this, to let you know, I watch your videos every time something is hard. If someone asks me for advice of some good courses to improve their knowledge, I recommend them your channel ! You make awesome videos and are a part of why I get straight A's and ace my exams. Keep it up # Fuse School - Global Education !

[juliedaily]

Love this! :) You do need to fix your chromosomes. A chromosome does not duplicate by making another one in the form of an X. The X is the duplicated chromosome. That will need to be adjusted and also that will change when it is in each cell (no longer an X). I hope you update this!

[gibriljallow]

Straight to the point.
Great explanation. Thanks

[SharkRockstar]

I love you FUSE SCHOOL!! YOU'RE A PART OF LIFE :3

[bradensinclair]

This video is to brief and doesn't explain DNA replication to a sufficient amount of detail.

[ayushmansaha]

You have made complicated subject easy

[marianaleaver]

My mom: No no no ur beautiful

How I really look: 0:18

[queen]

could you please create a playlist for higher combined science :) your videos are amazing loving the graphic designs!!

[MrJeroenB]

I believe the video is incorrect in showing what pairs are. What you show at 1:00 is not a pair, but 1 chromosome consisting of two chromatids connected by the centromere. A pair is not connected, except during metaphase in meiosis I.

[ClansThega]

If only he could emphasize on some words like 'complementary', 'template', 'RNA' .
I had to rewind a lot of times, infact I could have explained better. A better in depth with special emphasis would be much appreciated.

[SuperPopse]

In our class the teacher uses this video as a horrific bad and flawed example :D

[kyleg]

"For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord."-Romans 6:23

[MeneerSpoor]

I don’t think this is correct. First of all, you show a pair of chromosomes that are fused together like two chromatids, which are not one pair but two copies of one chromosome.
Secondly, the 3’ and 5’ sides of DNA are ignored and DNA polymerase is showing reading both from 3’ to 5’ and 5’ to 3’, also ignoring Okazaki fragments. I can’t show this to my students.