Science for kids - What is DNA ?

Have you ever wondered why every one of us looks like our parents? You can thank, or curse DNA for that, the magical stuff that makes everyone
of us, us.

Narrator :
Ayush Sinha

Acknowledgements:
www.sciencefocus.com
www.openclipart.org
www.flaticons.com

Script:
Today we’re going to learn about DNA.
Let’s start by putting this all into perspective. The human body contains 30 trillion cells, and in all of these cells lies a nucleus.
Inside every one of these nuclei, there are 46 chromosomes, which are thread like structures made up of DNA. These chromosomes are arranged in pairs.
We have only shown 3 pairs of chromosomes for simplicity in this diagram. Each one of the 2 strands on each chromosome is made up of two strands of DNA interwoven around each other in a double helix structure. Every cell in your body contains the same chromosomes made up of the same DNA.
Did you know that if you stretched the DNA in all of your cells out, it would make a length of string twice the diameter of our solar system. Isn’t that amazing? And somehow, we manage to compress this gigantic length of string into our comparatively tiny human bodies.
So what actually is DNA? DNA is the stuff that makes everyone unique. It has a hand in pretty much everything about you, from the size and shape of your face to the colour of your eyes. In fact, DNA doesn’t just stop there. It can be broken down further into sections called genes.
A gene is just a certain part of your DNA that codes for a particular trait. You could have genes for eye colour, height, hair colour, etc. DNA is what biologists call your genotype (what your genes say) and it decides how your phenotype is expressed (how you look from the outside).
STRUCTURE OF DNA
Now let’s take a look at the structure of DNA.
But first, we need to understand what a polymer is. ‘Polymer’ is a Greek word, ‘poly’ meaning ‘many’ and ‘mer’ meaning ‘unit.’ Now can you guess what a polymer is? That’s right, it’s just many of the same small units repeating one after another. DNA is commonly referred to as a polymer. The small molecules that keep repeating in DNA are called nucleotides, which can be broken down further into 3 parts.
A sugar called DEOXYRIBOSE, a PHOSPHATE and a BASE.
There are 4 different types of nucleotide, and these are determined by the base. The sugar and the phosphate always stay the same in every nucleotide, but there are 4 different bases that they can be attached to:
Adenine [A]
Thymine [T]
Cytosine [C]
Guanine [G]
Now, there’s just one last thing you need to understand about these bases. Do you remember what shape the DNA is arranged in? You guessed it, a double helix structure.
TO BE DISCUSSED
Each of the 2 strands of DNA in this helix is made up of nucleotides, joined one on top of the other by their phosphates. In order for these 2 strands to connect to each other, they have base pairs that always bond to each other. Adenine always bonds to Thymine and Cytosine always bonds to Guanine. This formation is called complementary base pairing.
You can think of this as a ladder, with the 2 long poles on either side being the phosphates lined up and each rung being either half adenine and half thymine or half cytosine and half guanine. Once this ladder has been constructed, it is twisted to form the double helix structure of DNA.
Now let’s get back to the question we had at the start of the video. Why do we look like our parents? Well, that’s because half of your DNA comes from your father and the other half from your mother. So out of the 46 chromosomes you have in total, 23 are from your father and 23 are from your mother.
That’s why you will usually hear biologists refer to chromosomes in pairs, as the similar chromosomes from your mother and father are referred to as a pair.
Now that brings us to the end of this video.