Identify the statement which do not hold true for Deoxyribose Nucleic Acid.

A. Only purine bases are present in DNA.

B. Deoxyribose sugar is present

C. A nitrogenous base is linked to the 1'C pentose sugar through N-glycosidic linkage.

D. Phosphate group is linked to OH of 4'C of a nucleotide.

Choose the correct answer from the options given below:

A and D only

The correct answer is Option (1) -A and D only

In 1869, Friedrich Meischer was the first to identify DNA as an acidic substance present in the cell nucleus. He initially named it 'Nuclein.' It wasn't until 1953 that James Watson and Francis Crick, drawing upon X-ray diffraction data generated by Maurice Wilkins and Rosalind Franklin, put forward a revolutionary and elegantly simple model known as the Double Helix model to describe the structure of DNA. DNA is a long polymer of deoxyribonucleotides. The length of DNA is usually defined as number of nucleotides (or a pair of nucleotide referred to as base pairs) present in it.

 A nucleotide has three components – a nitrogenous base, a pentose sugar (ribose in case of RNA, and deoxyribose for DNA), and a phosphate group.

There are two types of nitrogenous bases – Purines (Adenine and Guanine), and Pyrimidines (Cytosine, Uracil and Thymine). Cytosine is common for both DNA and RNA and Thymine is present in DNA. Uracil is present in RNA at the place of Thymine.

A nitrogenous base is linked to the OH of 1' C pentose sugar through a N-glycosidic linkage to form a nucleoside, such as adenosine or deoxyadenosine, guanosine or deoxyguanosine, cytidine or deoxycytidine and uridine or deoxythymidine.

When a phosphate group is linked to OH of 5' C of a nucleoside through phosphoester linkage, a corresponding nucleotide (or deoxynucleotide depending upon the type of sugar present) is formed. Two nucleotides are linked through 3'-5' phosphodiester linkage to form a dinucleotide.

More nucleotides can be joined in such a manner to form a polynucleotide chain. A polymer thus formed has at one end a free phosphate moiety at 5' -end of sugar, which is referred to as 5’-end of polynucleotide chain. Similarly, at the other end of the polymer the sugar has a free OH of 3' C group which is referred to as 3' - end of the polynucleotide chain. The backbone of a polynucleotide chain is formed due to sugar and phosphates. The nitrogenous bases linked to sugar moiety project from the backbone.