RNA and Central Dogma

RNA

While DNA encodes instructions to build life, RNA molecule read and act on the information.
It simply copies the instruction and carry it to other parts of the cells to make proteins.
Recent understanding has shown RNA has much bigger role than acting as a messenger. (more on this later)
In terms of molecule, the only difference in RNA is an extra OH group which makes is unstable.
Thus, the major difference between DNA and RNA is that while DNA is more permanent RNA is not permanent.

The central dogma of molecular biology explains the how genetic information flows from DNA to proteins.
This simply describes how the code of life is brought to life.
This happens in two-stages called transcription and translation.
In short DNA is transcribed into RNA which is then read by ribosome to make Proteins which are the building blocks of life.
Note that advancements in biotechnology coincide with the increased understanding of the central dogma.

Consider DNA to be a cookbook of recipes for making proteins. Transcription is the process of photocopying the recipe. This is done by mRNA, short for messenger RNA, inside the nucleus.
Once copied the recipe mRNA goes outside the nucleus to the chef, called ribosome.
There is also a translator, tRNA who translates mRNA recipe to rRNA of the ribosome which then makes amino acids, the building blocks of proteins.
A block of 3 letters in the mRNA correspond to ‘cooking’ of 1 amino acid.
Each 3-letter base in mRNA that is read by tRNA that correspond to one amino acid is called ‘codon’.
Many amino acids come together to form the primary structure of protein.
The primary structure is twisted and folded to make a 3-d structure of protein.

The coding part of protein are called as genes.
According to recent understanding there are about 20500 genes in human genome.
Genes vary in complexity. They range in size from few hundred bases to more than 2 million.
98% of the genome is non-coding regions.