In the recent (two) years, this microscopic information carrier has continuously made headlines, yes, you guessed it right, I am talking about the DNA, mRNA; proteins and all jargons associated with genetic information. For all the enthusiast out there who want to know how the genetic code works; how a small strand is the master mind behind all the function in our body; and how because of this invisible (to naked eye) messenger we are better adapted and evolved.

If you view a cell (animal or plant) under a microscope (low powered) you’ll observe each individual cell with a thick dark dot inside them that’s the nucleus, which bares our genetic code. In plants and animals the genetic code is carried in the form of a double helix structure (imagine a twisted ladder) known as the Deoxyribonucleic acid or DNA. DNA generally are double stranded but are seen as single strands in some viruses for example Parvoviridae (class II viruses), but the two strand is more stable.

Prior to replication, you need some basic idea about what forms the genetic messenger, the DNA is made up of four smaller chemical molecule known as the nucleotide bases: adenosine (A), guanine (G), thymine (T), cytosine (C) and uracil (U) (that is present in the RNA molecule instead of the thymine base). Now, the beauty of all these bases are; they combine in a complementary fashion which in simple terms mean adenosine pairs with thymine (A-T)/(uracil pairs with adenosine (U-A) in case of RNA )and cytosine pairs with guanine (C-G). 

When a cell generally replicates, the genetic material i.e, the DNA is copied to two identical DNA molecules giving rise to 2 daughter cells. So, every time the cell divides, the 2 daughter cells consists of the same genetic information/DNA as the parent cell. When cell division begins, the DNA uncoils and one of the DNA strand acts as the template to be copied. The DNA does not uncoil at any random place but does so at a specific position that is called the origin.

For any process to take place preparation has to done, similarly for replication to happen the DNA has to be prepared, for this many enzymes and proteins aid in the process. Eventually, DNA polymerase a special enzyme assembles the new strand. The job of the polymerase enzyme is to add on the complimentary base pair to the template strands thus forging a new DNA strands for the daughter cells.

With this you might get a general idea about how DNA replicates but this happens only during cell division, but then, what does gene expression mean. Our genes carry the all the necessary information to make a functional molecule that is the proteins. So, in simple terms gene expression means generation of a functional protein from the genetic code. In the beginning, the information contained in the DNA is transferred to mRNA (messenger Ribonucleic acid) this process is called transcription. When transcription occurs, only that region of DNA that needs to be transcribed unwinds, just as before complimentary base pairing occurs and an enzyme know RNA polymerase catalysis the formation of the mRNA. However, here only a single stranded molecule is obtained once the mRNA is released. Next step involves the decoding of this mRNA to form the proteins, which is termed as translation. Again, the mRNA strand is read according to the genetic code, which links the DNA sequence to the amino acid sequence in proteins. This step here is what experts manipulate to reverse engineer a DNA sequence from amino acid sequence. Each group of three bases (U, A, G and C) in mRNA (remember we use U instead of T base pair in case of RNA) forms a codon, and each codon specifies a particular amino acid, a chain of such amino acids constitute a protein. Proteins as we all know it, are the main culprits behind every cellular function, they even aid in DNA replication and this how a gene is expressed.

In simple terms, DNA contains all the raw data, but the cell can’t comprehend it unless, it’s broken down and converted into a form that it (cell) can understand and thus deliver the desired result.

Evolution is the slow change to the DNA of a species over many generations. This occurs due to natural selection meaning when a certain trait help the survival and reproduction of an organism. Thus, helping the species better adapt in its environment and making them much more likely to survive and pass on the genes that aided their success.

Hope this article shed some light and cleared some concepts, although the processes previously explained, do take place with much more technical finesse but I know you got some gist about it and hopefully it helped.