DNA and Cytosine
Generally, all complex substances are made up of smaller building blocks, considering an example where our house is built with bricks, stones, woods, etc. and as the same; our body is made up of cells which form the basic unit of live. Likewise, DNA is also made up of smaller molecules which together functions as the important substance to live in.
We know that DNA is a complex molecule made up many substances like phosphoric acid, sugar (5-carbon) and nucleobases.
There are five nitrogenous bases which serves as the most vital and important component in the functioning of the DNA.
The nuclear bases are mostly of adenine, guanine, thymine and cytosine, and uracil in case of RNA.
These bases are generally classified into two types namely purine and pyrimidine. As every large molecule are made up of smaller sub units DNA is also made up of sugar and phosphate bonds and nucleotide bases.
One such nucleotide base pair is cytosine. Cytosine bases is one of four chemical bases present in the DNA, whereas the other three are adenine, Guanine and Thymine.
Inside a DNA molecule cytosine strands are located on one strand of DNA with the help of chemical bonds it pairs up with guanine in the opposite part of the strand. These sequences help in coding the genetic instructions to the cell.
Cytosine is first named by Albercht Kossel and Albert Neumann in the year 1894 from the thymus tissues of calf. The structure of cytosine as first described in 1903
What is Cytosine?
Cytosine is considered as one of the bases that are present in the nucleic acid of a molecule. Nucleic acids are usually composed of five carbon sugar bond which is combined to that of a phosphoric acid, with its nitrogenous bases deoxyribonucleic acid which is considered as an important hereditary material.
Such nucleobases are needed and found as most vital thing in all the organisms which is consisting of five carbon sugar deoxyribose with phosphate bond linked to it by a cytosine or other three bases to join together to form a complementary base with the guanine.
Where Cytidine is a structural and functional unit of ribonucleic acid which consists of cytosine and the sugar ribose.
Cytidine triphosphate an ester of cytidine and also with a triphosphoric is considered as an important substance that is utilized by the cells to introduce the cytidylic acid and further converts them into ribonucleic acids.
Cytidine triphosphate also reacts with nitrogen-which contains alcohols to form coenzymes which participate in the forming the phospholipids.
Chemical Nature of Cytosine
Cytosine is usually found as a part of DNA. Or of RNA. As a nucleotide in the form of cytidine triphosphate which acts as a co-factor of an enzyme and helps in transferring a phosphate to convert into adenosine triphosphate which is commonly referred to as ATP.
In DNA and RNA cytosine is paired up with guanine. However, in some cases if it is inherently unstable it changes its pairing to uracil which many leads to many disorders due to point mutation.
If it is not paired by DNA repair enzymes such as uracil glycosylase, it results in cleavage of uracil in DNA.
Cytosine is methylated and converted into 5-methylocytosine with the help of an enzyme DNA methyl transferase. And in some cases, cytosine is methylated and further hydroxylated to form 5-hydroxymethylcytosine.
Thus, cytosine is determined by the rate of deamination of cytosine and 5-methylcytosine which forms the basis of bisulphite sequencing.
Biological Function of Cytosine
When this cytosine is present in the third on the codon of RNA, Cytosine is present on the opposite side of uracil, since it is interchangeable with the third base.
If it is present in the second base of a codon. It is also interchangeable in the third codon which forms the serine groups like UCU, UCC, UCA, UCG.
Active deamination of the enzymes of cytosine or 5-methylcytosine in the family of APOBEC, of cytosine deaminase could have both beneficial and detrimental implication in various cellular processes as well as in the organismal evolution.
The implications that are present in the deamination of 5-hydroxymethylcytosine remains complicated.
Properties of Cytosine
Cytosine is considered as one of the important pyrimidine nucleobases with a chemical formula of C4H5N3O.
Pyrimidine is a heterocyclic aromatic compound and it is organic and forms single ring with the alternative carbon and nitrogen atoms. It has a molar mass of 111.10 gram per mole and a melting point of 320 to 325 ºC.
It can also be found as an important component in nucleoside base pairs and in forming nucleotides along with nucleoside and phosphate sugars.
Whereas in DNA and RNA cytosine matches with guanine which forms three hydrogen bonds while pairing.
Though cytosine is considered as relatively unstable it can be converted into uracil through the process of spontaneous deamination. This change can be correctly deamination.
This alteration in the nucleoside pair can be corrected by the process of DNA pair systems which uses the enzyme uracil glycosylase if this repair process is not being followed which results in point mutation.