Spacehey Science I: DNA, explained.

if you're friends with me on here, you might know that i sometimes post bulletins about science, more specifically biology and genetics. i chose to start a blog series so the texts i write will be preserved and more people can access this information if they need it or simply are interested. 

in this first entry, i will be talking about some basic things about the structure of the DNA so everyone who has a primary school level of biology can understand it. remember that i'm no professional, i'm just a 16 year old science student who likes biology so it won't be very complex stuff, but it's still reliable because all of this is coming from what i've been taught in biology class and from wikipedia.

i hope you enjoy!

i'm assuming you already know what a cell looks like and works, so i'll just jump right into the nucleus. i know this all is gonna be very long and maybe hard to follow, but i'll try to make it interesting to read and easy to understand, still you can ask any question you like in the comments.

okay so, most of the genetic material of a eucariotic cell is stored in the nucleus in the form of deoxyribonucleic acid, DNA for short. there's also something called ribonucleic acid (RNA), but i'm just gonna ignore it for now since it's much more complex.

if you zoom in on the nucleus, you're just gonna see something that looks like a plate of spaghetti or a yarn ball. that is the DNA, which presents in long chains. if you pay attention to the structure of the DNA itself (remember that it's a type of molecule!), you'll see that it kind of looks like double spiral stairs, and that shape is called double helix. we're going to look at what would be the ACTUAL stairs that you step on, what connects the two chains. those are called nucleotide bases.

there are four kinds of nucleobases: cytosine, guanine, adenine and thymine. i'll call them C, G, A and T for short. now the way that this works is that the nucleobases always go in pairs: A always goes in front of T, and C goes with G. this image shows it better:

even though it seems so crowded at first, just pay attention to those four letters, it's actually quite easy to understand!

the reason why this fact is so important is that it's the key to cell reproduction since it makes the DNA, which stores all the information about how an organism should work, very easy to replicate. if you only have one of the two chains, you can already know how the other one is like since the nucleobases are always complimentary, and the rest of the structure is always the same. and this is exactly how those letters are translated into real-life proteins that give us certain characteristics: the DNA splits in half, and one of the halves is used as a template for the RNA (which is consisted of only ONE chain with the same structure) to transport it to the ribosomes, which is where the actual translation into proteins happens.

since i know i've explained it like shit, here's a picture of a RNA molecule:

you might have noticed there's a new letter: U. it represents uracil and doesn't change the system at all, it just replaces the T, so anytime there's an A in the DNA, the RNA will have an U instead of a T.

and now that you've seen that the DNA is just a string, you might ask where do the x-shaped chromosomes come from, if they are related to DNA as well.

chromosomes are just very concentrated chromatin: a substance made up of DNA and other proteins. chromosomes are ONLY formed when the cell is going to divide into two (asexual reproduction), otherwise the cell nucleus just looks like the stringy spaghetti mess i mentioned earlier.

every species has its own unique set of chromosomes, which is called a karyotype. humans normally have 46 chromosomes in their karyotype, but there are certain species that have hundreds! chromosomes always come in pairs: there's always an even number of them because they're made of identical pairs. here's how a typical human karyotype looks like:

in this case it's a male, if it were a female there would be two identical big XX chromosomes.

but the karyotype doesn't look so perfect in real life! actually, the chromosomes are randomly laid out on the cell (REMEMBER! ONLY WHILE IT'S REPRODUCING), it's scientists who order them from biggest to smallest. even though there are so many pairs that look the same, scientists can know which are identical because each pair shows a different stripe pattern when the chromosomes are dyed.

if you've read all of this then congratulations! i just saved you like four 10th grade biology classes lol. i hope i didn't make it too long, hard to understand or boring. again, if you still don't get it i encourage you to ask in the comments or do your own research if you want ^_^ remember that this is just the first chapter of a series so stay tuned!!