Minor or Rare bases in RNA

An RNA has bases in it which vary in the amount in which they are present in the DNA. Minor bases are those bases which are present in the least amount and are modified normal nitrogenous bases. These minor bases are present in RNA as well as DNA. They join to form RNA by a hydrogen bond. These minor bases can be discovered in RNA as dimethyl adenine, kinetin, zeatin, isopentenyl adenine, etc. They are derived from purines and pyrimidines.

Overview of Purines and Pyrimidines

1. PURINES: Purine includes within itself bases like guanine and adenine, which distinguish ribonucleotides and deoxyribonucleotides. These nucleotides act as building blocks for the formation of DNA and RNA. They are present in meat and meat products. Purine is broken down by our body into uric acid, which is passed out of our body through urine. They also play an important role in many metabolic processes and signalling processes with the compounds, including guanosine monophosphate and adenosine monophosphate.

Purine is a weak acid and weak base. There are many naturally occurring purines like xanthine, uric acid, caffeine, theophylline, etc.

1. PYRIMIDINES: Found as one of the two classes of aromatic nitrogenous base found in RNA and DNA, which are heterocyclic in nature. In RNA, the two pyrimidines found are cytosine and uracil. It can also be discovered in many synthetic compounds like barbiturates, zidovudine, etc. The most simple member of the pyrimidine group has the chemical formula C4H4N2.

Many pyrimidine based compounds were discovered between 1837-1864, leaving their structure unrecognised. Compounds derived from pyrimidines play a very important function like the production of proteins, and amino acids, providing vital nutrients and boosting the immune system. They also play an important role in the development of drugs. The three pyrimidine nitrogenous bases act as the genetic material for all living organisms.

Types of minor bases in RNA

1. Dimethyl adenine: It is derived from purine. It can be defined as adenine, which is a tertiary amine which is substituted at the 6th nitrogen by the germinal methyl group. The average mass of dimethyl adenine is 163. It is capable of accepting hydrogen from a donor or bronsted acid. It works like antibiotics and inhibits the synthesis of RNA at the ribosome. No other species except rats, monkeys and humans are sensitive to dimethyl adenine.
2.  Kinetin: Kinetin can be defined as a class of plant hormones. It promotes cell division. It can also be defined as cytokinin, which induces the synthesis of RNA. Kinetin is also used in plant tissue culture. 
3.  Zeatin: Zeatin was discovered by Letham in 1963. Zeatin is found to be associated with plant and bacterial tRNA. Zeatin is an adenine-derived cytokinin. It helps in the synthesis of plant roots. It also helps in the growth of lateral buds when it is distributed on the meristem cells.
4. Isopentenyl adenine: It is an adenine derived minor base. It functions to regulate cell division, nutrient processing, and the development of cells in plants. It also functions to serve as a precursor for Zeatin synthesis.

Conclusion 

From the above information, it can be concluded that rare bases are the bases that are formed in the least amount or are derived from major bases like adenine, guanine, cytosine, etc. They may also be derived from purines or pyrimidines. Purines have the base guanine and adenine, whereas pyrimidines have the bases cytosine and uracil, in the case of RNA. The minor bases derived from urine and pyrimidines are kinetin, zeatin, isopropyl adenine, dimethyl adenine, etc. These minor bases are useful in functioning as well as providing advantages like control over tissue culture technology, cell division, etc.