Imagine that you want to build a robot.
You don’t know exactly how to do it, but there is a book in the library with instructions.
You go to the library and find the book, but there’s a problem. The library doesn’t allow
you to take the book out, and you can’t bring the materials to build your robot into the library.
So, what do you do? You decide to scan and print parts of the book to take back with you.
Now, you can build your robot! This is very similar to how DNA works.
Before we get into that, however, what exactly is DNA?
Quite simply, DNA is nothing but a giant molecule. “Giant molecule” might sound like an oxymoron,
but it’s a fitting description, considering that a single DNA strand can be as long as a human being—
up to 6 feet long! DNA is the molecule’s common name, but its proper title is
deoxyribonucleic acid. It has a twisting , helical structure, much like a twisted ladder.
Now, this giant molecule is made up of even smaller molecules. The sides of the ladder are
composed of sugar and phosphate molecules, while the rungs of the ladder are made with 4 chemical
“letters”— A for adenine, T for thymine, G for guanine and C for cytosine. These four
letters come in pairs that are destined for each other— A pairs with T, while C pairs with G.
This repeats on and on until we get a giant molecule of DNA.
If you think of the cell as a giant city, the DNA is stored in the nucleus,
which is like the library found in the head office of the cell.
DNA acts like an instruction manual for cells on how to make proteins,
which are the cell’s very own machines that literally run every aspect of the cell.
Proteins are made of tiny blocks called amino acids. There are about 20 different
amino acid lego blocks that are available to our systems. They join together in different ways to
create all the proteins that compose a cell. DNA can be read like a book, where you read
only the letter on one side of the DNA. The DNA is also read in 3- letter codes,
called codons. Each codon specifies a particular amino acid. Many codons together make up a gene.
DNA has thousands of genes that lay the groundwork for thousands of different proteins.
These proteins, with a few changes along the way, go on to make up cells, which in turn form
tissues, which subsequently form organs. All the organs, when put together, form a living being.
However, when creating these proteins, a cell might run into a little problem.
The amino acids are found in the cytoplasm, while the DNA is found in the nucleus. The DNA
isn’t allowed to leave the nucleus, just as you weren’t allowed to remove the robot-building book
from the library. The amino acids aren’t allowed inside the nucleus, just as you weren’t allowed
to bring your building materials into the library. So, to solve this problem, certain enzymes in the
nucleus do exactly what you did; they copy the DNA. This “copy” is called messenger ribonucleic
acid (mRNA), which the enzymes can smuggle out of the HQ and into the outer part of the cells,
where the copy can be used in protein workshops— the ribosomes.
Ribosomes are protein- building workshops in the cell. The ribosomes read the information
in the DNA, via the mRNA, in order to develop the final protein product. Thus , the ribosome
will read one codon and then add the correct amino acid. This process continues until the
instructions end and the protein is made. The resultant living being that is formed is
heavily dependent on the sequence and the number of DNA bases. The complete instruction manual for
human beings, for example, has 3 billion letters or bases. This complete DNA instruction manual
is known as a genome. Around 99% of the bases in the human genome are the same in all people. It
is the remaining 1% that makes each of us unique! Though scientists have uncovered how DNA works,
there is still a great deal that we don’t know. Building life isn’t quite like building a robot.
DNA, proteins and RNA interact with each other in complex ways to form and sustain living things.
DNA is also helping scientists investigate the history of life,
while genetic engineering might help us modify DNA in the future. Many of these processes are being
actively researched by scientists, and their ramifications could change life as we know it!
Clearly, this “blueprint of life” still has plenty of surprises in store for the world of science!