Question

How do nucleotides bond to form nucleic acids? State and explain several differences between the structure of DNA and that of RNA.

Answer 1

Hint: DNA is also known as deoxyribose nucleic acid. It is a blueprint to carry and inherit information from parents to offspring. It is a source of protein. Due to this the offspring resembles that of parents. It is genetic material in most organisms including human beings.

Complete answer:
- DNA contains several base pairs such as adenine, guanine, cytosine and thymine.
- Adenine bonds with thymine with help of two hydrogen bonds and guanine bonds with cytosine with help of three hydrogen bonds.
- The nitrogenous base molecule is joined to the sugar molecule by a glycosidic bond and forms a structure called nucleoside. The nucleoside combines with a phosphate group by an ester bond to form a nucleotide.
- In a nucleic acid a phosphate moiety (moiety is a part of a larger molecule or structure) links the 3' carbon of one sugar of one nucleotide to the 5' carbon of the sugar of the succeeding nucleotide The bond formed between the phosphate and hydroxyl group of sugar is an ester bond. As there is one such ester bond on either side, it is called phosphodiester bond.

Difference between DNA and RNA.

DNA	RNA
It is also known as deoxyribose nucleic acid.	It is also known as ribonucleic acid.
It has deoxyribose sugar present in it.	It has ribose sugar present in it.
The adenine pairs with thymine in DNA	The adenine pairs with uracil in RNA.
It is a double stranded helical structure and two strands are antiparallel to each other.	It is usually a single stranded structure. Only double stranded in rice dwarf virus and Reovirus.
Complementarity is present in them.	Complementarity is not present in them.
It follows Erwin Chargaff rule that is ratio of purine and pyrimidine bases is 1:1.	It does not follow Erwin Chargaff rule that the ratio between purine and pyrimidine bases is not 1:1.
It is present mostly in all organisms including human beings.	It is present in tobacco mosaic virus.

Note: DNA was first isolated in 1869 from the nuclei of white blood cells, because this material was found in the nucleus and was acidic, That is how it was named nucleic acid. There are more than a dozen forms of DNA named after English alphabets with unique structural features. DNA is mostly right handed.