The correct answer is option 1. Phosphodiester linkage.
Nucleotides are the building blocks of nucleic acids, such as DNA and RNA. Each nucleotide is composed of three main components: a phosphate group, a sugar molecule, and a nitrogenous base. The linkage between nucleotides in a nucleic acid chain is established through a phosphodiester bond.
Here is a detailed explanation:
1. Components of a Nucleotide:
- Phosphate Group: It is a negatively charged group consisting of a phosphorus atom bonded to four oxygen atoms.
- Sugar Molecule: In DNA, the sugar is deoxyribose, while in RNA, it is ribose. The sugar has a carbon backbone.
- Nitrogenous Base: There are four types of nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G) in DNA, and adenine (A), uracil (U), cytosine (C), and guanine (G) in RNA.
2. Formation of Phosphodiester Bond:
The phosphate group of one nucleotide reacts with the hydroxyl group on the sugar of another nucleotide. This reaction involves the removal of a water molecule, and it forms a covalent bond between the phosphate group of one nucleotide and the 3' carbon of the sugar of another nucleotide. The bond formed is called a phosphodiester bond, and it connects the 3' carbon of one sugar to the 5' carbon of the next sugar. This linkage repeats along the entire length of the nucleic acid chain, creating a sugar-phosphate backbone.
The phosphodiester linkage is crucial for the stability and structure of the nucleic acid molecule. It provides directionality to the chain, with a free 5' phosphate group at one end and a free 3' hydroxyl group at the other end.
In summary, nucleotides are joined together by phosphodiester linkages through a series of condensation reactions, forming the backbone of DNA and RNA molecules. |
