Okay, so I just came back from a biology lesson at school and we were discussing the structure of DNA. It isn't made up solely of proteins, carbohydrates or lipids. It's actually made up of nucleotides. At first, it may seem easy to remember but I was told that many people have strayed away from the beaten path regarding this.
What is DNA?
It's stands for deoxyribonucleic acid - can't imagine why they shortened that.
DNA is a chemical that determines genetically inherited characteristics in all living organisms. It is able to store vast amounts of information as a genetic code - hmm... what if we could use DNA to somehow store and access large amounts of information? It would be more compact and easier to transfer than our usual everyday data storage systems... Anyway, back to the topic at hand!
Frankly, DNA is ''sick'' - i.e. it's great. It's better than great: it is good (yeah, I reference Friends episodes from time-to-time, bear with me!). It is able to pass on characteristics between different organisms of adjacent generations - amazing.
Dude, I meant What is DNA?
Piccy time!
I'm sure you recognise it! I went to a lecture about DNA the other day: this helical structure is world famous - there are statues designed to look like this; there are coins that have this image symbolically engraved at the front: why? Because they look cool.
Biochemical components
One strand of DNA is made up of nucleotides.
One nucleotide (a mononucleotide) is made up of 3 components:
1. Deoxyribose sugar (C5H10O4)
2. Phosphate group (PO43-)
3. Organic base
There are 2 base groups:
1. Single-ring pyramidines: cytosine (C) and thymine (T)
2. Double-ring purines: adenine (A) and guanine (G)
When I first heard of cytosine, I confused it with cysteine - an alpha amino acid. I had to look at the first rule: DNA is made up of nucleotides - not proteins, carbohydrates or lipids!
Forming a double helix
Look at the nice picture of the DNA. There are little coloured lines in between those thick twisting tubes. They are the organic bases I mentioned earlier. Basically, they are base pairs that join up together. One base group always bonds with a base in the other group.
E.g. a purine like adenine will only bond with a pyramidine like thymine.
Why should this happen? Basically, each rung of the DNA ladder must be the same length. It is always three rings in length. So a double ring will join with a single ring so that the total length is always 3 rings across. Pretty neat, huh?
HOWEVER, adenine, a purine, will not bond with cytosine, a pyramidine. Why? I mean, cytosine is a pyramidine... confusion much?! :(
If you know a lot about enzymes then you know that substrates are complementary in shape to them. In the same way, antigens are complementary to antibodies. Again, in the same way:
A is complementary to T and forms two hydrogen bonds
G is complementary to C and forms three hydrogen bonds
In chemistry, hydrogen bonds are amazingly strong intermolecular forces.
In biology, when compared to disulfide bridges in an antibody (and cysteine and methionine proteins) and ionic bonds, hydrogen bonds are proper weak.
DNA is a really confusing topic - people have told me that the main reason is because they sometimes forget the basics or didn't understand DNA from the start. It's really hard but maybe reading this blog has helped you!
This post is mainly a response to my fellow students who told me that they were finding it difficult to comprehend so much in a single hour's lesson - so I hope this helps anyone trying to understand the fundamentals of... well... life!
I'll try to find some articles that concern DNA before my next post. Don't forget to give me feedback too :)
Exocytosis
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