Is it like precise like a computer reading data or more down to some cells just happen to react to a particular part of a DNA which starts off some process?
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It’s closer to a computer program.
DNA that’s just sitting there doesn’t do anything. In order to influence the cell it needs to be “unzipped” (split into separate strands) by specialized enzymes so that the DNA can be “read” and used to create proteins. How & when which parts of DNA get read and do something is called epigenetics and it’s *super* complicated, but what each section does is very concrete…different sections of DNA code for different proteins.
DNA is the “recipe book” for your cells.
The key component of DNA is the **nucleotide.** This is a little molecule that comes in 4 flavors. You can consider these the “letters” in our recipe book.
These letters form three-nucleotide sequences called **codons.** A codon is basically the “word” in our recipe book. It codes for what’s known as an **amino acid.** You can think of these like building blocks for building components of the cell.
If you string enough of these “words” together, you get a **protein.** A protein could be considered a “recipe” in the book. These proteins do many of the life functions that the cell needs to survive.
This recipe book is kept in the **nucleus** of the cell. Now, you don’t want to damage the master recipe book. In order to avoid that, proteins called **polymerases** make a copy of the recipe they want to create. This process is triggered by signals in the cell. It’s like a kid asking for a specific meal; if they ask enough times, you’ll probably make it, if you happen to have a lot of carrots, you’ll probably use a recipe that uses carrots, etc.
The form that this “copy” takes is called RNA. This is slightly different from DNA, but the same general idea applies in that it’s made of nucleotides and stuff.
Once a copy of the DNA is made, it is “read” by a thing called a **ribosome.** This piece of the cell sees the codons in our copy, reads what the “word” is, and grabs an amino acid (our building blocks) that the word represents. It then moves to the next “word,” grabbing and attaching this amino acid to the one before. Repeat this 1,000 times and you have a long string of amino acids.
Depending on the characteristics of these amino acids, they will form a protein with a particular shape and function.
DNA consists of chains of molecules called nucleotides. Each nucleotide is made of a sugar, called deoxyribose, a phosphate molecule and one of 4 different nucleobases (designated “A”, “C”, “G” and “T”. The sugar and phosphate attach together end-to-end and form the backbone of the chain: phosphate – sugar – phosphate – sugar -… The nucleobase attached to each sugar is what encodes the information in the DNA. Of the four nucleobases, there are 2 pairs that like to stick together, they are called complementary. Each DNA molecule has two chains that stick together because they have exactly complementary nucleobases at every position and coil around each other to make the familiar double-helix shape.
A cell interprets DNA by building proteins, according to the instructions encoded by the DNA. Proteins themselves are chains of molecules called amino acids, so there’s some natural analogy to DNA.
To make a protein, the DNA is first copied to a messenger molecule, called messenger RNA or mRNA. mRNA is very similar to DNA. To make the mRNA, the DNA double-helix is unwound and an enzyme called RNA polymerase binds to a specific region on the DNA that tells it where the sequence coding for the protein (galled a gene) starts. The RNA polymerase helps RNA-nucleotides floating around in the cell to bind to complementary nucleotides in the DNA and thereby form a complementary string of RNA. This RNA string is terminated where the gene ends, so only contains the information required to build the specific protein. The mRNA produced is now used to build the protein:
There are 20 different amino acids that your body strings together to build proteins, and each amino acid is coded for by a sequence of 3 nucleotides. So when the cells reads the sequence ACG it knows to use amino acid X, when it reads GTC, it uses amino acid Y. The sequence ACGGTC would tell it to string together XY in the protein. This pairing of 3 nucleobases to each amino acid is called the genetic code.
Inside your cells, there are molecules called transfer RNAs or tRNAs. They consist of 3 nucleotides and an attached amino acid, precisely that one which corresponds to the 3 nucleotides, according to the genetic code.
An enzyme-complex called the Ribosome attaches to the mRNA we produced in step 1 and lets the tRNA floating around bind to the mRNA. The tRNA is complementary to the mRNA, which in turn is complementary to the original DNA and thus the tRNA corresponds exactly to the original DNA sequence. The ribosome then takes the amino acid off the tRNA. Then the ribosome moves 3 positions over, the next tRNA attaches according to the sequence and the Ribosome takes its amino acid and attaches it to the amino acid that is already there. This repeats until the entire mRNA has been parsed and we are left with a long chain of amino acids that matches the sequence in the gene in our DNA. This is our protein.
I’m sorry for the wall of text, but this is a pretty complicated process and, in fact, in reality, it’s even more complicated.
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