How does genetic information pass among DNA, RNA, and proteins?
Genetic information, once created, can be replicated: information is stored in DNA and DNA can replicate itself; DNA is also inherited. Thus genetic information passes from one generation to the next in the form of genes on DNA .
Genetic information is 'expressed' when there is transcription of gene on RNA and then there is subsequent translation of protein.
Genetic information passes from parent organism to progeny organism through asexual or sexual reproduction. In both the cases genetic information is written on DNA.
DNA may travel to next generation through gametes , in case of higher organisms. Fusion of male and female gametes would produce the first cell of next generation.
On the other hand, an organism can grow and develop through gene expression. For this the organism must produce unique proteins. Recipe of proteins are written on DNA as genes. Such recipe must be copied on RNA and accordingly a protein would be translated.
Once the DNA gets inherited by a cell, the genes (=sequences of DNA where recipe of proteins are written) present in it must express as and when the products (=proteins) are needed.
To express itself, codes of a particular gene must be copied on a single stranded RNA. It is like copying one recipe on a single page from a huge cook book. Code written on this messenger RNA is read by ribosomes of cell cytoplasm.
Both DNA and RNA uses nitrogenous bases as letters and genetic words/codons are written as three-letter words. Such triplet codons represent 20 amino acids. There are 61 such codons: each codon, universally in all biological organisms, represents one particular amino acid.
Sequences of triplet codons written on mRNA are translated as string of amino acids, joined one after another by peptide bonds. Formation of polypeptide, initial form of a protein, is assisted by ribosomes.